To avoid characters in Arcade mode (except Bison) have a second player press 'Start' and select a character and then beat them. You will now no longer have to fight that character. Doing this will prevent you from you from unlocking achievements.

Complete the following achievements to unlock the corresponding number of Xbox Live Gamerscore Points. There is a total of 200 possible points

I Got Next - 5 Xbox Live Gamerscore Points:
Play a match in the Online Quarter mode.

12 World Warriors - 5 Xbox Live Gamerscore Points:
Fight with ALL 12 characters in Single-player Arcade mode.

Perfection - 5 Xbox Live Gamerscore Points:
In Single Player Arcade mode complete a perfect match at the default or higher difficulty setting

Bonus Bonanza - 10 Xbox Live Gamerscore Points:
In Single Player Arcade mode complete a perfect bonus round .

10 tokens - 10 Xbox Live Gamerscore Points:
Play ten ranked Online matches.

World Champion - 15 Xbox Live Gamerscore Points:
Compete Single Player arcade mode.

50 Tokens - 20 Xbox Live Gamerscore Points:
Play 50 ranked Online matches.

10 Ranked Online Victories - 20 Xbox Live Gamerscore Points:
Get 10 wins during ranked online play.

7 Stars - 20 Xbox Live Gamerscore Points:
Complete Single Player Arcade mode at the highest difficulty level.

Hyper World Champion - 25 Xbox Live Gamerscore Points:
Complete Single Player Arcade mode without losing a match.

Perfect World Champion - 30 Xbox Live Gamerscore Points:
Complete Single Player Arcade mode without losing a round.

30 Ranked Online Victories - 35 Xbox Live Gamerscore Points:
Get 30 wins during ranked Online play.