Brainwashing and amnesia! And nightmares! And hiding an illness/injury! Bullet wounds! Medication! (Heh -- PoI already did those last two. ♥)

I'm vaguely twitchy about self-harm (because it tends to manifest in fanfic as BSOs cutting themselves like teenage girls) and sexual extortion (again, in the context of fanfic, I associate with Aliens/Sadistic Villains Made Us Do It). But I can't see you writing either of those examples, anyway!

Feel free to help yourself to all three, if you'd like.