I really don't think Blixer is star level in his first form. I'm assuming that kinda like the supreme kai and Beerus from dragonball, the sun and the tree are linked (ie destroy one you destroy the other) which is why Blixer could destroy the sun by just ripping it out of the ground. At the end of the game the Tree of Life restores the sun which was destroyed at the begining, putting it at around star level when all 3 pieces are combined.
