A wizard did it! Magical other world has gravity which turns off when it’s convenient for the main characters! I suddenly know magic when it’s convenient because the magic was in me all along!
So jumping the shark (I think it’s called that) is one.
The magic was in you all along! Yeah, then why did all your friends have to die, if the magic was in you all-a-bloody-long?!
The power of friendship/love (excessively). Like when it’s used clumsily to defeat the main villain, with no set up, or any kind of reason for it to work (like fusion in Steven Universe is a good example, because it turns normal sized people into these giants, and it was set up early on)
Well, that’s a list of tropes I hate, sorry if it’s too long