Sharks kill to eat it's nothing personal, just the rules of nature.
Dolphins on the other hand will bully smaller fish for their own amusement.

Sharks: I'm gonna sneak attack this seal and critically wound it in order to guarantee a quick kill so that I can eat.

Orcas: Despite being larger and more powerful than any predatory shark, I'm gonna beat this litte seal to death over the course of an hour because it's fun.