Hannyabal

Hannyabal is the vice-warden in charge of Impel Down. He often self proclaim himself 'ambitious'.
He is also extremely eager to replace the current chief warden, Magellan, such that he often slip his tongue when speaking, saying he wants to be the warden and to replace Magellan directly in conversations totally unrelated to the issue.

He is willing to allow criminals to escape so that he can put the blame on Magellan and replace him as the Chief Warden.