@Chaotic Chao: Racheli's based off several comic book characters, from Magneto to Venom.
Gambit's powers, from my understanding, are where he charge the card/objects (in the cartoon anything could be charged) then it had a set timer before it exploded. Sometimes it exploded on impact. His powers are also gained from being a mutant, someone born with it, which how your PC got his powers might differ. Was he exposed to radiation, dowses in chemicals during an accident, OD on a street drug that gifts powers, or something else? As Dedonus stated, just because you have the same powers doesn't make them a carbon copy. Racheli would've been considered a carbon copy of Magneto then if that was the case.
Another suggestion is take a look at the way others have done theirs. You'll be able to pick out the influences, similarities to other heroes/villians/etc in comics but also how they differ. That's my best advice.