The 'so cool and awesome' character who has apparently never failed at their special skill before, and the first time they do- ususally against an opponent that's been shown to be stupidly powerful and has beaten several others before you, they instantly fail every time they try that skill again until they go and train again, usually back where they first trained, and suddenly they're brilliant again. Case in point, Crystal from The pokémon adventures manga, we had 2 books show her to be great at catching pokémon, then suddenly she fails to capture Suicine, a freaking near legendary pokémon, and we waste the first 3 or 4 chapters of the next book having her go back to training. Also any character that 'teaches people a lesson/ help them become stronger' by doing hurtful things to a character, case in point Professor Oak from Pokémon adventures, who is the worst character ever (Congrats, you entered a tournament designed for kids, beat a bunch of them thus destroying their dreams, and traumatised a 10 year old girl just to teach her a lesson!), and Vriska from Homestuck, who is a close second. (Yes, clearly smashing somebodys legs is going to make them stronger, as is blaming them when they're unable to go up the stairs you made, instead of ramps like any none jerk would do)