It is said that he killed his entire family with a machete when he was nine years old. He is also a cannibal. As such, everyone in the prison is afraid of him. During the zombie outbreak, the Banoi Butcher slaughtered every prisoner and guard (Including Mario) in the same area of the prison as him, so the other inmates locked the entrance to that area to prevent him from escaping and killing them as well.
He is the primary focus of the side quest"Banoi Butcher", in which the player must find him and kill him in order to put the other prisoners at ease.
Banoi Butcher (post-patch)
“You think I'm fucking crazy, don't cha? But it's the world that's fucking crazy. Not me. I'm just fucking hungry!” — The Banoi Butcher
Being a human, headshots will do massive damage, being also able to kill him instantly.
He will not attack the player until they enter the room or, as of the latest patch, until an attack is initiated on him provided he is not killed in the immediate aftermath (such as utilizing the molotov tactic detailed below but opting not to follow up with a firearm).
Attacking using an automatic rifle is rather effective.
The easiest way to defeat him is to use your Fury move on him. If your Fury is melee-based, just pummel away while dodging him. If your Fury is a ranged attack, you can just stand back and attack him from a distance.
An easy way to defeat him is to simply wait until the door opens, then toss a Molotov at him. As he is thrashing in the flames, get in close with a shotgun or automatic and open fire.
Another easier way is with a shotgun, let him approach you and just when he is about to swing, shoot at his head, killing him and leaving a bloody corpse.
Possibly the most effective way to kill him is to simply stand outside the door and shoot him in the head.
Standing outside the door and shooting him with a shotgun is incredibly effective, though becomes easier with the Shock Shotgun Mod equipped.
Another easier way is to throw a knife (with the Sticky Bomb mod) at him. Avoid his attacks or back off until he explodes into a bloody corpse.
In the original released version of the game, the Banoi Butcher was no tougher than any other human enemy, and thus died very easily despite his boss-like status. After the latest patch, the Banoi Butcher has been made into a more challenging opponent, roughly on par with a special infected such as a Thug or Butcher. He now has about 5 times as much health as a normal human enemy, is resistant to knockdowns, and his attack now deals about as much damage as a punch from a Thug.
His combat behaviours are very similar to Jason. It's also interesting to note that they're both cannibals.