[quote=@BreakingMe]
I put effort into a CS to make my char a realistic but entertaining person. Then the GM posts their CS [i]after[/I] mine and their char is so desperately a Mary Sue that I debate myself - to run or not to run. 
[/quote]

If you're not confident, then say an apology and pull out. No point being in an RP that could be overpowered by the GMs character. In saying that, it depends what the GM has installed for the future and their overall vision.