Madara Problem
The Madara Problem is when a character is so strong, they can’t be killed, and the writer is stuck trying to figure out how to kill them without making them look like a joke or using a stupid trick.
I had to kill my main character with a laser from a robot that showed up out of nowhere.
My villain was too strong, so I made him die from a fart from a talking cat.
I had to kill the strongest character in my story with a single punch from a guy who just walked in.