Pirate seems to be the easiest, followed by Cat and Witch. Cookie is a brutal hitter for Stage 2, and your pirates are cheap enough to contest the board early as long as you don't over-commit before his turn 7 nuke. Cat is a constant supply of minions with the power and things like Infest, letting you recover fast from a pumpkin or Fear. Witch struggles early game, where killing pumpkins is crucial - late-game is its forte, with all of its taunts and healing and self-bounce options to re-establish control.