One character has Flow which allows him to manipulate solids by injecting said Flow into them. Fair enough. The weakness? Well, instead of being something you might think like the larger the solid the hard it is to manipulate it or something like that it's not - every solid seems to be affect in the same way. The true drawback is that he can control all solids bar plastic and rubber...
Said character is now also subject to a stolen subplot that someone else came up with.
Nathan's use of Psychic Powers when he had them. He had become unbeatable because he could pull them outta nowhere whenever he pleased. He's now lost his ability to use his Psychic Powers though, so things have once again balanced out.
The most prominent example is probably Nathan. Some just seem him as the arrogant Smug Snake that is in desperate need of having some sense beaten into him whilst see him as an interesting character who brings something fresh to the the RP as a whole.
Sabina is either a character you'll love or you'll despise.
Crossing the Line Twice: Nathan does this once or twice. Especially in his training fight with Luke. Poor bastard...
Game-Breaker: Nathan and Joey are probably among the better examples but there are others.
Nathan's actually getting a lot better seeing how he's lost pretty all the abilities he had any measure of true skill with and is back to square one in terms of his learning curve.
Justified with the Big Five in that they're adults and are suppose to be a great deal more powerful than the contestants by default because of this. Joey, who has now also become an adult, would also get away with this justification, however, his ability seems to have little to know visible drawbacks that are of any real use that have been used on a regular biases whilst all his other known weaknesses, for lack of a better way to put it, are rather retarded.
Level Breaker: Certain powers make certain challenges ridiculously easy.