A client asked that I add a new character to the pitch bible that I'm writing. Without going into detail, I'll say that its an interesting character - but unsuited to the stories they're trying to tell.
This guy is all powerful with tremendous resources at his disposal. BUT --
Is he a good guy? Is he a bad guy? How does he fit with the Good Guys' dynamics - or on the Bad Guys team? How does he affect the balance of power in the show? Huh? "Balance of Power"? What's that?
Referring to The 21 Things a Broadcaster is Looking for in Your Script or Pitch post from last year, Number 11 says:
There should be a balance between the forces of good and evil. Even if the good guys are vastly outnumbered, the audience should have some hope (however faint) that they will succeed in their quest. Otherwise, what's the point?
In the case of my current writing assignment, the client had asked me to add a character who's powers and resources vastly outstrip those of the protagonists and antagonists. It's like grafting an H-Bomb onto Shaggy's right hand. That gives him tremendous power. Suddenly "Scooby Doo" is a whole other show. (I had the idea of grafting an H-Bomb onto Gilligan's hand - and with that, "Gilligan's Island" REALLY becomes a "whole other show". I may just pitch that one...)
Back on subject - At the beginning of Star Wars (Episode 4 - for the nerds), Luke Skywalker is no match for Darth Vader. However over the course of the trilogy, his abilities grow and he defeats Vader - there is a balance because the threat of Darth Vader forces Luke to grow - so that he reaches his potential. If Vader could (and he can - but he chooses not to) snuff out Luke Skywalker then there is no balance in the storytelling. It's all one sided and unsatisfying.
Balance or a shifting balance - keeps the characters and storytelling interesting.