This is when a character gains the ability to walk through walls or become bullet proof or go back in time and then forgets it for the rest of the story or in the sequel When basically 80% of the problems they encounter could be solved by it… And you're mentally screaming at them “Use your damn power that you got 20 pages ago… Remember that thing that would help you avoid all this trouble!?”

Using easy solutions to get out of problems causes plot-holes! And your audience will hate you for it.