From movies to video games, the Achilles heel of most fictional bad guys is just how damn arrogant they are. There are countless examples of villains who think they're the smartest people in the room, more powerful than anyone else, and so above everything that they'll get their goons to do most of the dirty work for them. In their heads, there's no reality in which they lose, as they're destined for greatness.
Of course, in reality this often means they're complete idiots.
Even though video games have birthed plenty of memorable heroes across the years, strong enough and smart enough to take down even the toughest foes, in many cases it's the villain themselves who are their own downfall. Their evil plans were in reach, inches away from being fulfilled, only to be dashed at the last minute by a major lapse in logic.
From plans so convoluted you have no idea why anyone thought they could ever work to dangerously underestimating the protagonist at every turn, sometimes video game antagonists are their own worst enemies.