These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Marty Stu: Averted. Even with powerful characters, including one with all 999/999 stats, the author figures out how to present a challenge to the main characters. Mainly by putting them up against other overpowered characters.