Not consciously, of course. But there's this nagging feeling that Steve should have looked for him when he fell off that cliff, and everything that happened results from him NOT doing that. So he can't shake the feeling that it all could have been prevented.
So maybe when he's having an especially bad memory, or when he sees the other Avengers being happy and cozy and he thinks "this could have been me", he sort of lashes out by sharing a particularly bad rape/torture memory. Maybe the first time he does it is by accident, but he catches on what effect this has.
Double bonus if they're in a relationship.
Triple bonus if Steve feels guilty for the same reasons and that makes it all the more awful.
Quadruple bonus if Bucky ends up saying something so awful he instantly regrets sharing it, but he can't take it back.
Bucky, on some level, blames Steve
So maybe when he's having an especially bad memory, or when he sees the other Avengers being happy and cozy and he thinks "this could have been me", he sort of lashes out by sharing a particularly bad rape/torture memory. Maybe the first time he does it is by accident, but he catches on what effect this has.
Double bonus if they're in a relationship.
Triple bonus if Steve feels guilty for the same reasons and that makes it all the more awful.
Quadruple bonus if Bucky ends up saying something so awful he instantly regrets sharing it, but he can't take it back.