I mean yes, he looks like a horrible monster, but in the cartoon he is constantly eating rocks, which is tantamount to cannibalism. He looks like a monster and so he is a monster.
Pulver-Eyes might not be pretty, but he is unique. He's a horrible (heroic) monster, with a lot of interesting (weird) things about his design. He might not be particularly fun, but he's got a certain "Oh my god what the hell is that?" quality about him that is charming in its own right. Also his name is hilarious.