Pull a Rorschach
To pull a Rorschach get oneself killed (by another) so that they do not have to do something morally right that would likely cause large-scale problems for their friends/acquaintances/the general public.
Bob: Hey guys, have you seen Jim? After I told him I robbed that bank, he left my house and I haven't seen him since.
Jeff: Jim said he had to tell, but because he didn't want to rat you out, he said he was going to pull a Rorschach.
Bob: Oh my god, that's horrible!
Jeff: Jim said he had to tell, but because he didn't want to rat you out, he said he was going to pull a Rorschach.
Bob: Oh my god, that's horrible!