I've had a handful, "epic" might be a stretch for most of them (dramallama being a better descriptor), but one stands out.
There was a man, [Redacted] whom Stecker had grown to trust entirely. They'd been dating for a good while and she finally decided he should see the ugly violent side of her so he could make a more informed decision about whether to keep dating the dangerous psychopath. So she tells him to shackle her and then hit her or otherwise piss her off, thus causing psychological and physiological shenanigans (oh god what a terrible character I made).
The problem is that he's a gentleman, and refuses to hit her. So she tells him to do something to piss her off.
So instead he explains that while she's been restrained, he has poisoned her, using a poison created to target her specific genetic makeup. It was such an amazing betrayal of trust, and so incredibly well played, that it had me shaking OOC at the same time that Stecker was losing her shit IC. Needless to say, once [Redacted] had seen everything he needed to, he explained that it was all a lie.
This, ofc, made Stecker that much angrier, that he had decided to be such a "gentleman" that he would tell a devastating lie rather than hit her, despite the fact that it would be infinitely more damaging. It took her a while to forgive him.
Anyhow, the betrayal was so thorough and well played that it remains one of my most distinct memories from EVE RP even after I've been away from the game.