King Arthur Fallacy

The belief that a society simply needs to elect the right leader and give the leader all the power they ask for, ignoring that 1) a leader who makes one group happy will hurt another group, and 2) the powers given to the one good leader will still be in effect when their successor takes power.

Person A: "You don't get it! If we can just ignore the Constitution and give (politician) more power, they'll fix everything!"
Person B: "That's the King Arthur Fallacy! As good as King Arthur may have been, he's at the very least mostly fiction, and all the kings that followed still wielded his power, for better or for worse.