Wasted Villians

What villains or antagonists had their potential wasted? Ones that you believe were pretty lame and didn't live up to the hype.

I grew up watching The Clone Wars and Steven Universe.
General Grievous was ASS throughout the whole series. Only time he was EVER intimidating was when he butchered the Nightsisters.
The diamonds were hyped up as these unstoppable goddesses but they were actually just a bunch of oversized crybabies (especially White Diamond).