Levi will never forget about being quirkless, how weak he felt. How helpless he was in most situations. No matter how hard he trained or how much work he put in, there was always going to be someone who had a quirk to counter him. Sure most quirks were not all that powerful, but Levi wanted to become a hero. And once he awoken something inside him that made him an endgame level threat, he for sure was ready to put it to good use.
9 parts