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This is so common, the trope is usually going to be related to the reason.
Power at a Price, Dangerous Forbidden Technique - Their superpower has a dangerous cost or downside.
Coconut Superpowers - Showing their power is expensive, so it can only be done sparingly.
This Looks Like a Job for Aquaman - Their power is so specific, it can't be applied to most situations even if they wanted to.
Fights Like a Normal - Another option, even if their powers are related to combat, that they seem to prefer fighting with martial arts.
Thinking Black Canary