It wasn't really Blork's fault he was a brat. It was the piece of eggshell that got stuck behind his ear the day he was hatched. It made him cry. But baby Splatoons aren't supposed to cry. So Blork got a brat label stuck on his head.
Soon Blork really was a brat - the worst on the planet Splat. And he learned to throw tantrums better than anyone else on the planet. But even a mega-tantrum can't save Blork's pet poodnoobie the day it's taken away by the Big Pest Squad.