As a counterpoint to my own post - allow me to clarify something.
I'm not saying that the OP (or anyone else here) does this, but it is important to distinguish between a "problem player" and a well-designed, highly skilled character. Characters should be allowed to succeed on their own merits - if the player is using their brain and playing to their characters strengths, there is nothing wrong with them succeeding. Heck, if their character is really THAT GOOD, they should make it look easy...most of the time.
At a certain stage in GM development it is not uncommon for a GM to adopt an "us vs them" philosophy, wherein they feel that if the PCs are succeeding all the time, then there is a problem with the scenario or with the players. The key is to remember that the GMs job to make the game FUN - there is a balancing act of challenge vs reward that must be maintained, but at the end of the day...the hard fought day...the PCs should (if they play smart and well) succeed.
If you determine that there is a problem and that a character must be dealt with, it must at least APPEAR to be within the letter of the rules. Yes, GMs can bend and break rules as they see fit, but you DO NOT want to screw directly with a PC while doing so.
Example - back in the day, playing CP2020 (SR without happy Elves...or singing birds, for that matter) I built a pretty durn good Street Samurai (called a Solo in CP). He wasn't over the top, cyberzombie, Instoppatroll or anything - he was just tough, skilled, fast, aggressive, and most of all...TACTICAL. After many sessions, the budding GM observed that my Solo was impervious to most small arms.
I made the argument that he had paid a steep price to become so - Humanity (Essence) loss for all the cyberware, money for the custom armor, etc.
To the weefle GM, though, he saw the Solos ability to stop a 9mm with his skull as a threat to the game balance, so he took action - knocked the character out with a drug and stripped him of all Cyber.
Problem was not only that he did it, but how he did it. He had a non-combative semi-aquaintence scratch him with a neurotoxin laced ring. The Solo had boosted reflexes and mad kung fu skills and specifically stated he wasn't letting the weirdo get near him, had skin that would stop a katana (let alone a needle) and had specifically built in anti-toxin blood filtering Cyberware to stop this exact sort of poison.
My character's first act upon waking up, sans cyber, was to commit suicide. Not as a player tantrum, but because that PC had based his entire personality around being a superhuman Cyborg. In RP terms, it was his entire sense of self.
So - long story short - before dealing with a problem player, make sure they really are a problem, and if you take action, do your homework. The reason I am usually so quick to suggest killing a PC in this situation is that is often LESS sticky than maiming the character and taking away an ability that is a core concept for the player.
/rambling diatribe
-Jn-
Ifriti Sophist