edThe most aggressive monkey is the Drill. This large monkey is native to West Africa and is one of the most ferocious primates in the world. They are extremely territorial and hostile to anything that enters their space, and will not hesitate to attack people, even if they are unarmed.
They have large canine teeth which they use to bite and show aggression towards potential predators. Additionally, the Drill uses a unique honking sound as a warning mechanism for others in its troop.