Chimpanzee
While many people don't look at a Chimpanzee and think "danger" these animals are tough and built of pure muscle. One chimpanzee, that lived in confinement, ended up attacking its caregiver. The chimp randomly attacked the woman, biting and tearing at her flesh and nearly killing her. The woman lived, but she had to undergo numerous surgeries to reconstruct and mend the wounds caused by the animal.