I read some of my earlier posts, and man do I need to edit myself more better. :/
Sometimes you might discover that there is something...wrong with your game. Something is constantly cropping up and is making it difficult to generate effective and compelling plots. Something may be causing player friction. What could it be?
Perhaps it is a character.
Your player might be a great guy. He may be a great role player. But is his character monkeying up the works and ruining your campaign? Maybe. Here are some signs that a character may be the source of your problems:
Too Powerful: This character makes the rest of your team look like scrubs and it feels as if he might be able to solve all the problems singled handedly and is only holding back to spare his team mates' feelings. Superman might have days like this. Too powerful does not necessarily mean raw might, it could also mean too versatile. Hi tech, cosmic and magical characters could both suffer from a little too much versatility where their power sets are concerned. I used to game with a guy named Nick in my Champions RPG days, he ran a character named Quantus. I inherited this character from a previous GM who allowed Nick to abuse the character creation rules to such an extent that Quantus was a nightmare. His ridiculous speed and power set meant I kept having to create more and more powerful bad guys to give him a challenge, which meant the rest of the PCs suffered as a result. In the end I gave up when Quantus single handedly stopped the main bad guy and his entire team of badass minions single handedly.
Too Weak: Are you handling a PC with kid gloves? Do villains inexplicably leave him alone during combat? Or is he/she constantly getting hurt or kidnapped and placing the other PCs in peril as a result? Maybe the character's power levels are too puny for the campaign world. Batman makes keeping up with demigods look easy, but when your writer is Grant Morrison that is only natural. Not everyone can pull off being a powerless or low powered character in a campaign world where everyone else possesses god-like might.
Genre Incompatibility: Your player approached you with a novel idea, a character that was going to be refreshingly different. Perhaps he/she is a mage in a wild west setting. Or is a steampunk scientist serving on board a Starfleet vessel. Maybe he is the only character in the Potterverse packing heat. Initially it sounded like a neat idea, only now...
Well, this neat character that would have been great in a novel is just driving you nuts. Heat packing Potterverse character just put a bullet in the head of your principle villain, or Steampunk engineer is useless on an away mission. For one reason or another the character's way-cool weirdness is making thing difficult for you.
Too contentious: Conflict in a game is not always a bad thing. Characters who get along all the time can be boring. So when a player wants to play a character who does not play nice with others that is not a bad thing. The player wants to role play and that should never be discouraged.
But maybe his style is a little too...passionate. He adheres to the letter of the law too literally, or is a casual killer in a team of law abiding heroes. He/she hates another character and cannot resist an opportunity to needle his nemesis whenever possible. One way or another, the character is harshing everyone's mellow.
So, what do you as the GM do? If you let the player run this character it is partly your own fault. That does not necessarily mean you are a bad GM. You did not want to say "no" to your player, or he/she was a great salesperson, or your blood sugar was low that night when you wrote that e-mail agreeing that yeah, Starhammer The Undying would be a great addition to your wild west campaign. Or you were desperate to fill out your ship's roster and were willing to let the guy play Anything, even that Q/Borg hybrid, to swell the ranks. Whatever the reason, you have a problem on your hands and must fix it.
If the character is too weak or too powerful, you either work with the player to adjust their power levels. You could make the power change an adventure in itself; perhaps the uber powerful character has to sacrifice a measure of his might to stop the bad guy, or the weakling adopts the weapons of his fallen enemies to augment his abilities? If the character still has potential then work with the player to keep him. If the character's idiom simply does not work in regards to your game's tone/theme/setting, then it might be time to get rid of them altogether. If a player is contentious to the point of distraction, then they need to adopt some sort of in game reason for them to start playing ball with the other characters. It could even be an amusing reason; years back in Justice League megajerk Guy Gardner was knocked out by Batman and when he awoke he hit his head. This resulted in a complete personality change.
But perhaps your player is sticking to their guns. Your player insists their character is fine the way it is and they refuse to change or retire them. They are refusing to work with you and might even go so far as to say they will quit if they cannot play their character. When that happens, it is time to either stop the game or fire the player. Remember this; you are not being paid to be a GM (If you are, please let me know how. I would love to get in on that action), you are running your game on your own time because you want to, because it gives you pleasure. If this character and his player is making the game feel like a job then it is time to reassess your relationship, game wise.
Finally, as I said in an earlier post, it is very important to hold your temper. If things get heated then take a step back, calm down, find your happy place again. You never want to say something that might damage a friendship.