Source: comicvine.gamespot.com

4. Amygdala

Aaron Helzinger was a violent giant committed to Arkham Asylum.

An Arkham Surgeon removed the amygdala cluster from Aaron's brain, hoping to cure his psychosis, because that is just the sort of bats**t insane quackery one could expect from the fine folks at Arkham Asylum. The surgery just made him WAAAAAAAAY crazier and WAAAAAAAAAAAY more violent, so that was a big problem for anyone facing him.

Bane broke him out during Knightfall, and he teamed up with the Ventriloquist before getting beaten up and sent back to jail. Over the course of a few years, Aaron formed a friendship with Dick Grayson, aka Nightwing, and redeemed himself. He was almost blown up by Blockbuster, but survived, and was last seen hanging out in the Iceberg Lounge having fun. Amygdala is a peak 90s Batman villain, and I love him.

Dude just needs more love.