"James destroyed the one person he loved most in a moment of blind passion.
That's not something you forgive."
I O N L Y H A V E E Y E S F O R Y O U, 2x19
Or, Buffy's Relationship With Forgiveness
I Only Have Eyes For You is one of the most underrated episodes and I am going to tell you why. Not only on the Bangel(us) front (because, let's be real, why are people still arguing about whether or not Angel loved Buffy without his soul? Did they watch this episode?), but on the froth of Buffy's entire characterization. This episode sets the tone for one of her most compelling character traits: her overwhelming capacity for forgiveness.
First and foremost, let's talk about the primary issue and character arc of the episode.
The tone is set by the first scene: Buffy turns down a guy who would like to go to the Sadie Hawkin's Dance with her (and who also apparently doesn't understand the purpose of a Sadie Hawkin's Dance), and makes the claim that "I slept with him, he lost his soul. Now my boyfriend's gone forever and the demon that's wearing his face is killing my friends. The next impulsive decision I make will involve my choice in dentures." There's a lot of self-blame packed into this line, which is one that doesn't get a lot of emphasized screentime. She doesn't blame Angel for what he's doing, even now. She's putting it on herself for taking his soul from him, by making the "impulsive" decision to sleep with him -- she feels she's being punished for it, and more than that, she feels like she deserves to be.
Buffy refuses to forgive herself for unleashing Angelus, who just killed Jenny Calendar two episodes ago, and subsequently 'killing' Angel more or less. It's not just Angelus' actions she's taking blame for; she accuses herself of destroying the person she loved most in a moment of blind passion, perceiving it as thoughtless, impulsive and unforgivable.
This leads to her over-identifying with the ghost of a boy (James) who killed the teacher he was having an affair with, and she denies him forgiveness as well, belligerently demonizing him so that she can take out all of the hate she has for herself. Giles, acknowledging this self-loathing train for what it is, puts a stop to it with this quote:
She doesn't take this to heart easily, of course. In fact, at first, it only spurs her on, and she says he (and, effectively, she herself) doesn't deserve forgiveness, no matter why they did what they did, no matter how sorry they are or whether or not they know now that it was wrong, because they just have to live with it.
She has to learn through the ghost of the young boy what it feels like to be forgiven by playing through the scenario with the possessed Angelus acting as Angel, forgiving her for destroying him, and the feeling of that weight having lifted makes her really understand what is so important about it. She tells Giles that she doesn't understand why the woman would forgive the ghost that possessed her -- why Angel would forgive her -- and Giles makes her realize it doesn't matter. It's not the why, or the how that matters. It's that you have to love someone enough to find a way to forgive them, because that person, that person that you love, needs it.
It makes this colossal difference in her, to be alleviated of that burden, and it prepares her for what she has to do (kill Angelus) because she's no longer burdened by the guilt of bringing it onto Angel. This also marks another important point about Buffy and forgiveness: she has a harder time forgiving herself for her crimes than she does with any other person.
But, she takes this lesson, and she carries it forward with her, setting the tone for many of her future relationships in canon. Even when Giles later would try to advise her against it, Buffy keeps this in mind and continues to be the bigger person, a person who is capable of unbridled, unlimited forgiveness.
When Angel regains his soul three episodes later, and doesn't remember anything that he's done, she forgives him for what he's done as Angelus. In just an instant, she is overwhelmed with so much relief that it's him that she doesn't even think twice about it, and she calls back to it in Amends when she tells him "I know everything you did because you did it to me" and "I wish that I hated you." She still has elements to her of the Buffy who held her stubborn grudge against Miss Calendar and only began to open up to her again before she died, and she wishes that she could let her stubborn ability to hold a grudge carry out, but she doesn't.
She has so much love for Angel, for everyone, that she forgives him for what he's done because she doesn't know any other way to be. Angel tortured her psychologically for months, emotionally ruined her, killed her friend, and she just forgives him for it. Unlike most everyone else in the Buffyverse, Buffy doesn't really distinguish between Angel and Angelus. She calls him Angel the whole time, because he is. She doesn't trick herself into thinking they're separate people, she acknowledges that it's him, just without his soul, and that's why it hurts her so much. Because she does love him, and it feels like without his soul he has just stopped loving her (a misinterpretation on her part because she doesn't understand soulless vampire's feelings, or see him waxing poetic about her to Drusilla and Spike).
But, none of that matters. None of it matters the second his soul is back, none of it matters the second she sees him back from the hell dimension. She sees that he needs someone who forgives him, because he clearly isn't going to forgive himself, and she makes it clear that he did it to her so that he's aware that she is the one who has the right to forgive him. It's not easy for her to do, and it hurts because he was able to hurt her so much because of how much she'd loved him while he did those things, because she knew it was still him, but he needs it, so she selflessly gives it as a way of trying to save him.
(For more on Angel, such as Twilight, see: 8x40 - Last Gleaming Part V.)
Blah blah stuff about Faith which is really complicated because Buffy did do everything she could to try and help Faith, gave her every chance, and forgave her in Graduation Day even after trying to kill her to save Angel. She tried to reach out again in This Year's Girl, willing to put all of the past behind them in order to help her, but she spat in her face and rejected it. Buffy never forgave Faith for Who Are You, so it's tough.
Then, there's Willow. Willow, who turned into the greatest force of evil the universe has ever known because she is the single most powerful being in all of Buffyverse, who tried to end the world in an Apocalypse, threatened to turn Dawn back into a glowy ball of energy, and killed a man. Buffy doesn't think twice about forgiving her. She offers to forgive her before they even fight, during the fight, after. She has reached a point where she isn't interested in even trying to hold a grudge, Faith has left an impression and instead of being reluctant to grant forgiveness or granting it out of obligation, she is urgent for Willow to accept it.
She's beginning to understand. She never stops trying to get through to Willow, not once, and when Willow comes back, because if she does give up, she'll lose her forever. When Willow comes back in Same Time, Same Place, even though Buffy has to suspect her as the gnarl out of her Slayer duty, she doesn't want to believe it, because she has forgiven Willow for Warren, she just hasn't forgotten what she did, because Buffy doesn't get the luxury of doing that. And, when it turns out Willow is okay, that she isn't the baddie, the awkwardness between them dissipates in an instant -- the instant that Willow realizes that Buffy has forgiven her entirely. And their friendship
And by now you've probably noticed that I've put one off until last and that's because Spike is going to be the longest to explain. Forgiving Spike is something that a lot of people think that Buffy isn't completely capable of (usually accompanying a belief that she'd never got here again), or something that they want to scorn her for doing (rape apology), and it's just overall really touchy for obvious reasons.
Spike tried to rape Buffy. He sexually assaulted her. Despite the way the shooting script paints it, physical attempt at violation is still a violation, whether he succeeded in getting inside of her or not. He violated her in her own home, where she was supposed to feel safe, right when she had finally rediscovered her strength and her will to be a part of the world, right when she was finally feeling safe back in the hard, bright, violent world of the Buffyverse that she wanted to escape from to return to Heaven. He took that safe place away and reaffirmed exactly why she thought the world was Hell in the beginning of the season. The final act of a desperate thing. He was driven by selfishness: desperation, desire, loneliness and loss, because he wanted to possess Buffy in a way that she wouldn't let him, so he was going to take it for himself because he lacked the moral compass to tell him why he shouldn't.
And that's exactly what makes Buffy capable of forgiving him. He could not possibly conceive of why what he was doing was wrong. He didn't have a soul. No soul, no conscience, no moral compass, nothing to tell him that he was bad and should feel bad. But, he does. The second she kicks him off of her, he feels it. Remorse. Guilt. The overwhelming truth of the fact that what he is doing is wrong. Despite having no soul or capacity for good, he awakens to the monster inside of him and sees it for what it is: something bad that hurt someone he loves. Hurting someone he loves is bad. It's not good anymore. It's not their game of hurting one another and getting off on it. He has surpassed his own capacity for morality, stepped above it, stepped outside of his own natural selfishness, and seen himself for what he is: evil.
She doesn't forgive him for it until she sees that he's done this. She gets a glimpse of it when she's too wrought with horror and disgust in the bathroom to really see it for what it is, and then he tries to play it off for two episodes, but she finally sees it at the end of Beneath You. She sees his penance. He doesn't insult her by apologizing, not once, because as sorry as he is, he can't bring himself to ask for her forgiveness because, again, like Angel, he doesn't forgive himself.
He needs it. He needs to be forgiven so that she can tear him down like she does in Get It Done and stop him from being afraid of himself and his capabilities. He needs it to regain his sanity. When they're in that Church in Beneath You, she sees his penance and she sees his self-loathing and she sees that he will never forgive himself for what he's done, and he couldn't live with it then so he went to get a soul to be what she deserved, and now he's even more incapable of living with it.
He's punishing himself enough for the both of them. She can forgive him, and he can carry the burden of knowing what he did was wrong and knowing it hurt her, because he is never going to forget, and she has faith that he will do so, trusts him, despite everything that he's done, to be a better person because of it.
It could be argued that her forgiving him is a matter of interpretation of that scene and the following scenes in the next ten episodes or so, but by the second half of the season she outright states that she trusts him. She trusts him not just with her own safety, but with a house full of girls who she's charged with protecting. The safety of herself, the safety of others, and she trusts him enough to remove his chip and state outright (something she has a hard time doing in general after Angel) that she does. If she hadn't moved past him hurting her and forgiven him for it, she wouldn't be able to trust him so absolutely, particularly when you factor in that she has specifically told Angel numerous times that she doesn't trust him at all.
So, with the argument has been made that she DOES forgive him, he makes for the cherry on top of all her other forgiveness. It's not that she's just forgiving him for starting the Apocalypse, or killing someone, or things that are done to other people. He turned her personally into a victim in her own home, and she finds it in her heart to forgive him for it, and it is just so important to who Buffy is that she has this seemingly endless capacity for forgiveness. She's a big enough person that she can step outside of her own personal sentiments, and her own hurt, and be above that in how much she loves others.
There are other cases, of course, who she has to forgive for more minor offenses.
She forgives Giles in Helpless for violating her by drugging her without her knowledge. For using her and treating her like some kind of test subject instead of like a person, the way the whole Watcher's Council does. Just like all the above: she sees that it tears him up inside. She sees that he hates himself, that he can't stand what he's done and that it hurt him to do it, and that he's sorry. So, she forgives him.
She forgives Riley for getting suckjobs from two-bit vampire whores. In order to completely understand how big of a forgiveness this is, going to these vampire hookers is effectively the Buffyverse metaphorical equivalent for infidelity. First of all, the blatant calling them whores. Second, the speech he delivers to Buffy in Into the Woods about how they need him on a primal, basic level, and how he is getting his emotional needs fulfilled by them in a way that he isn't getting it fulfilled by his relationship with Buffy. And, the second she realizes she's at risk of losing him, the second she understands why he's done this, she gets more sympathy than rage -- hours after finding out -- and she tries to chase after him, ready to open her heart more completely than she's ever opened it to him and actually, no holds barred love him.
She doesn't even ask questions when Xander leaves Anya at the altar and disappears for days. She just welcomes him with love, forgiveness and acceptance. As she tells Anya: what he did was wrong, and he knows it, and he feels terrible. So, she forgives him. And then she forgives him for his poor, hurtful reaction to Buffy's secret affair with Spike. He treats her like crap for it, and she just readily welcomes him as soon as he's over it with absolute, unquestioned forgiveness for his behavior.
Learning how to not hate herself and not hate Spike was instrumental in tempering Buffy's ability to hold grudges. In the way that she knows how to put them aside and not bother with them anymore. So, when Robin tries to kill Spike and almost interferes with her entire world-saving plan, she doesn't give him flack. She's straight with him. She doesn't hold it against him or act mistrustful towards him. She gets why he did it, she forgives him for doing it, but she's not going to deal with it a second time.
In short: it all comes back to what the First Slayer tells Buffy in Intervention: she is full of love. It's brighter than the fire, and she forges strength from the pain it brings her. The strength to continue to love, give, and forgive. She has the capacity to forgive anyone who is willing to seek it out, to be truly repentant and to be strong enough to fight for it.
She has high demands, high expectations for people seeking it, which is proven by Faith, because she demands that they understand the gravity of their crimes, that they hate themselves a little for it the way she does for hers, the way Angel does for his, the way Spike and Willow do for theirs. But, she has unlimited forgiveness that she is willing to grant to anyone she loves, regardless of what transgressions they commit.
Even when others think it's unwise for her, even when she maybe would be smarter to not forgive them, she does. Even when Giles, who spurred all of this on in her with his words of wisdom, tries to tell her not to give it, she is the bigger person and does anyway. Because they need it, and she understands what that need for forgiveness feels like and how it can eat you up inside.