Bruce gets captured and raped and maybe tortured by one of his villains (maybe Joker? but I have no preference, though I'd prefer if it was a guy, and please no permanent injuries). Of course he pretends afterwards that he's perfectly fine, that his wounds just need to heal and then he'll be back on his feet, he's not traumatised or mentally scarred or whatever, nope, not him.

Of course it's bullshit and he's actually even more of a fucked up, nightmare-riddled mess than before. Clark wants to help, but he's not sure how to get through to Bruce. Established relationship is fine, them being just allies/friends and only getting together after this is fine, too.