All you really have to do is attack him.
I've played with him, and against him, albeit only with Ressers. With Doug, it's as easy as two, possibly three actions to kill him. With Nicodem, I simply paralyze him, then throw punk zombies on him. Another thing is throwing Whispers From Beyond on him from the Hanged, which negates all healing on him. That hurts most strategies involving Izamu. I know from experience that Collette just laughs at him with Dissapearing Act.
If anything, I think Izamu is going to make Resser players worse at the game by using him as a massive crutch. He's good, yes, but he can and will die. And when he's dead, that player is going to flounder, even if playing Yan Lo. That 10+ Crow isn't always going to be in your hand.
I'm actually not that big of a fan of Izamu. I love him with Yan Lo, but would rather take the Dead Rider in most situations with our other Masters.