After his country was destroyed, the events caused him to become omocidical and nihilistic, not wanting to believe anymore and wishing to destroy the world as much.
He and have an extremely close relationship, having met in Swallow Island during their childhood and Law protected the bear mink when he was being bullied by Shachi and Penguin.
Big Mom seemingly did not take the two Supernovas seriously until he and Kid managed to her.