At this point, it's a little difficult to tell, given that both parties are dead. I don't think it was an equal partnership, by any means, but I have heard that Kane came up with at least a FEW brainstorms - the characters of the Penguin, Catwoman and Two-Face, for instance, are supposed to have been created by him, I think. At any rate, he put a hell of a lot more thought into the character than Liefeld put into Deadpool.