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I don't know if there's a trope for this, but if there is I would think that Bucky from Captain America: Winter Soldier would count. He blames himself for things he did while he was being controlled.
These ARE the droids we're looking for. That was lucky.
The example in the OP doesn't help much, since I'm not familiar with the series it's from, but it sounds like the characters involved were Unwitting Pawns.
A pawn/patsy/whatever's hand can be forced either directly, or indirectly. It's also possible for the person using them to not even speak with them, especially if the pawn's own decisions works to the user's advantage.
Edited by MiinU
Sounds like Cartesian Karma to me.
I'm trying to look for a trope in which certain people are made to do some certain set of actions, but they can't object nor defy anyone because they physically cannot. The trope is different from Morton's Fork and Forced to Watch because in this situation, it's not a villain or somebody forcing their hand, they just can't do anything because they didn't have the means to and were used however someone wished, and the people using them are genuinely oblivious to their free will because it's not apparent.
For example, in Bakamatsu Tenrouden, the main characters sing about how as inanimate objects they were used however they liked by their masters, but they still carry a lot of guilt over what they were made to do (such as being isolated for display or being used as a tool of war).
Edited by lalaTKG