Grunty just really isn't a very good pet. None of his abilities really stand out that much. He does have a multi hit attack that hits an extra time if he goes first, but his speed is terrible. He certainly isn't a pet you can build a team around, all of his abilities are fairly basic. The one thing he does kind of have going for him is he has a few mech abilities. Most humanoids can't deal much damage to beasts, but Grunty sure can.