Prison is a completely different world from the streets. No guns, knives, or bombs. Are there any mobsters known to be tough guys who instilled fear in prison?

No one inmate can install fear into that many inmates in a prison, there are too many tough or crazy people inside those places. Now, as for mobsters who were tough, and may have scared a few inmates, there are many. It's mostly a matter of protecting yourself and having a enough influence with other inmates groups to get by and be treated respectfully.

Lilo, for sure. Also, Chin.

When Cain was imprisoned, he was in trouble with some black inmates because he was a cop, but when Outfit capo Willie Daddomo stepped in, all of the black inmates backed off and never dared to touch Cain ever again, although those were the days when the Mafia was still at the top of US OC.

....on the other hand during the 1940s, while in jail, infamous Outfit capo Phil D'Andrea was almost beaten to death by KKK prison guards because D'Andrea threatened the prison doctor, and some sources speculated that when D'Andrea was released in 1947, there was allegedly some retaliation but I still cant find any hard evidences or details about that same claim.

Ernie Abbamonte was a Gambino made man that spent all his life doing in and out of prison drug telated offences and in 1982 was sentenced for intruducing heroin in prison. I dont know how was feared but for sure respected for be a stand up guy a good earner because for sure was working with other inmates.

Mike Rizzitello had a good relation witj pegleg morgan a legendary mexican mafia shot caller so for sure he was respected in California prison.

You must remember most people in prisons who are extremely violent need psychological therapy but unfortunately are just thrown in a cage. You could be the toughest motherfucker around and they still would attack you. They don't fear anyone and actually love receiving pain along with giving it.

If you were to hit them as hard as you could they would actually enjoy it. You could smash their face in and they would literally start laughing in your face no matter how bad you hurt them. They are sick and are not programmed as a normal person.

This is why they are locked up.

People often make fun of John Gotti for getting knocked on his ass by that black guy, but to his credit, he didn't seek protective custody. That's respected in prison.