The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
You may want to see the aptly-named Powerful, but Incompetent.
Another angle is Unskilled, but Strong, like a mage who has a huge amount of raw talent but their only spell is "fireball". It's a really good fireball, but still lacks a certain versatility.
A Great Gazoo can also be played like this, where they have incredible powers held back not by incompetence, but their immaturity or desire to use their powers for cheap pranks and trolling.
Wow, this is a marvelous response; I'll take a look at all three, though it appears the first one is exactly what I was looking for. Thank you!
What’s the trope for when a character’s abilities are exceptionally powerful, but they’re kept in check by the character’s incompetence?
Edited by Notsofriendly