Seamus Costello/Sean Doyle
The OIRA and Jim Flynn in particular come in for a lot of flak for the death of Seamus Costello. Flynn is alleged to have pipped him while he sat in his car on 5 October 1977.
He was a handsome man and seen by many as a lost leader. But the people who think he was some great hero of the left should know he was utterly detested by the Provos who they also seem to venerate. The likes of AIA and the general leftist-republicans.
But of course the OIRA has never claimed responsibility for the killing. Most people don't seem to know that. But even more don't know it's (allegedly) untrue that Seamus Costello even died. He faked his own death with the OIRA as part of a deal to wind down the INLA. There was some respect for Seamus still in the OIRA/Workers Party, particularly as the OIRA softened its stance and turned even more anti-republican/armed struggle.
Costello left Ireland for a while and returned with the name "Sean Doyle". He popped out of nowhere, but now he's involved in republican commemoration/soft activism. Interesting man.
That's what I've heard anyway. I don't have any firm evidence. It's hearsay.