For the one that is not familiar with this trope related to a character:
The character is a powerful magic user or has a strong superpower, but to stop them from being too overpowered, they are phisically frail.
The game here is finding reasonable excuses for this aside from "there are no gym classes in wizard school". After all, if they are adventurers they may expect being in danger.
I will start:
Excuse1-:Age: the character is a kid, or too old, which makes them phisically frail. A kid haven't developed their phisique and that means that they are at a disadvantage in direct combat, and an old person, while they may have more experience, their bodies are way past their prime and lost a big deal of their strenght, agility and stamina.
Alright, now is your turn!.