There are certain animals that you can't imagine ever doing anything mean or nasty. In this bracket I would place sea lions. After staffies, they have the cutest faces on earth.
However, it turns out they are cruel killers when they want to be. Check out this never-seen-before footage of sea lions attacking and eating giant floppy octopusses. The sea lions drag them to the surface so they can breathe while they slowly bite off their tentacles one at a time. Jeffrey Dahmer would be proud.