To the death in a plain arena. Kratos has all his weapons from god of war 3, Deadpool has all his weapons.
In a battle- Medusa head, or Kratos rips his soul out.
In terms of game wise-
Deadpool got pretty bad reviews and critism.
It relies too much on the humor(which is mostly one-liners and fourth-wall jokes), and is a very mediocre shooter game. I mean you have to REALLY like Deadpool to find this game good.