Big Boo (Paper Mario series)

Atomic Boo is a Boo made up of hundreds of different Boos combined. When a bunch of Boos attacked and clung onto Mario in Creepy Steeple, Mario knocked them away with his Spin Attacks which angered the Boos alot. They then combined together to attack him. Atomic Boo attacks by flinging Boos at Mario and using a charged up screaming attack. He/they can give Mario a bunch of different stat problems.

Atomic Boo is similar to Boolosus in in several ways.