They revealed a lot of his skills in the reveal video. a lot of his skills revolve around boosting melee and explosive damage. The right 2 trees are focused on melee and elemental damage. One of his skills gives him a bonus for being on fire and another has a chance of igniting him.
One of his game changers let's him change his FFYL mode. He can run around while in FFYL and suicide for massive damage and a potential second wind.
Some skills gives him a boost for taking health damage.
Oh, you thought they made this game for you? You clearly bought the wrong game.