Two... least that I knew of.
One was young when he was part of a duo (the other was a gang killer - never knew him) who killed a guy and buried him in some forest. They young guy served his term and that's when I first met him. He was so damned straight and intent on remaining that way the rest of his life and is married with a family.
The other was... well, a sad case all round and in his 50's when I first met him. He had spent his whole life murdering people for a well-known "team" (who by that time were all in a jail cell or dead). Dunno how many people he actually murdered - but it's 99% certain it was more than he was ever convicted on. He has spent most of his life in and out of jails on murder and related offenses.
Oddly, when he was released from jail, a friend gave him a job managing a store - based on the logic he would not dip his hand in the cash register - "petty theft" was beneath him
The guy is not the most intelligent of people - he was "used" by others all his life to do their dirty work - and he did it.
So... this store is kinda upmarket and the clientelle were wealthy old ladies with blue-rinse hair blah... John gets dressed in a very smart suit for his new job and actually performs pretty well. He calls the customers "Mam" and "Sir" and becomes very polite :-)
But.. there were these notable moments when his roleplay slipped.. One was on a rainy day and this elderly lady with blue-rinse hair was about the enter the store - so John proceeds to open the door and take her umbrella. She says, "It's a very wet day". John replies, "Yes, it's a fucking foul pissing day Mam" I don't think that lady actually believed what she thought she was hearing.
But otherwise John was the cream of public relations.
After a few years, he obviously met up with old friends who by that time had stopped murdering people cos they found the drugs trade more profitable. And, once again, John was used to, dunno exactly, but carry some drugs, and ended up in jail once more where he died of cancer.
In the interim, he ended up marrying a lady in a *very* high and respectable position (can't say here) in an international organisation. The pair of them could not be further apart in background or education, but they seemed happy enough.