Full list of all 15 Fighting Vipers achievements worth 400 gamerscore. It takes around 1-2 hours to unlock all of the achievements on Xbox 360.
Destroy a stage wall in Arcade Mode or Offline Versus
Use Mahler in Arcade Mode or Offline Versus (at chara select, move cursor left of Grace, hit OK)
Select game settings in Arcade Mode while holding ↑ to unlock Candy's appearance in 2nd Attract Mode
Hold↑and hit START during Attract Mode in Arcade Mode
Select game settings in Arcade Mode while holding the X button to enter Attract Mode
Complete Stage 4 of Arcade Mode (any difficulty)
Complete Stage 3 of Arcade Mode (any difficulty)
Play Ranking Mode in Arcade Mode (hold down P+K+D+START during Attract Mode)
Select game settings in Arcade Mode or Offline Versus while holding LB+RB to activate Kids Mode
Win a round without receiving any damage in Arcade Mode (any difficulty)
Complete Stage 2 of Arcade Mode (any difficulty)
Break an opponent's armor in Arcade Mode or Offline Versus
Complete Stage 1 of Arcade Mode (any difficulty)
Unequip armor in Arcade Mode or Offline Versus (quickly input →←→←+P+K+D)
Arcade Mode: unequip Candy's armor each stage, or destroy Candy's lower armor 10 times in a row