Villain power cliche-
"Ok, I have this really cool tricky power which so far has messed up my opponents at every turn- but I'm going to turn it in for an even greater power: Getting really strong and/or big!"
This leads to the defeat of so many villains because it makes beating them *simplier*, the hero now only needs to figure out how to hit them really hard, and even in the odd case where they'd lose anyway, it makes the fight more boring.
The tricky power can be illusion, speed, some form of telekinesis/control power they use to make a giant body, etc..