Whether it’s the main bad guy or someone lower in the chain, which villains in games were ultimately a detriment to their own scheme or that of an allied bad guy? Who was their own worst enemy? Maybe they shot themselves in the foot, maybe their plan was fundamentally flawed, maybe they were just complete morons that would have done themselves in without our input, but where either way the protagonists of the story had little to do with something falling apart, or might even have failed without an antagonist screwing up.
ARTHUR! I HAVE A PLAN! immediately scuttles off to start coming up with a semblance of a plan