This is a lot of incarcerated supervillians to take in, I realize. In the first panel, from left to right, they are:
Professor Brainfever (from Chris Morse’s excellent Supervillain Corner podcast)
Zoot Suit Brute
Big Papa (also from Supervillain Corner)
Jack (a soldier of fortune with a bionic arm, from one of J.R.’s Dr. Mercury stories)
Panel 2 has Cockroach getting grub with Headcannon, and that’s Sir Ringe again in the background.
Cockroach seems to have made an enemy of Rock Lobster in panel three. That’s Jack in Cockroach’s corner, and Cyberback behind the both of them.