Here is the full list of all 50 The King of Fighters XII achievements worth 1,000 gamerscore.
KO'ed every character in Arcade Mode using all of the characters.
KO'ed every character in Arcade Mode using Elisabeth Branctorche.
KO'ed every character in Arcade Mode using Chin Gentsai.
Achieved Rank SSS in Online Mode.
Achieved Rank SS in Online Mode.
Achieved Rank S in Online Mode.
Won 100 or more battles in Online Mode.
Achieved Rank A in Online Mode.
Achieved Rank B in Online Mode.
Achieved Rank C in Online Mode.
Competed in 300 or more battles in Online Mode.
Won 50 or more battles in Online Mode.
Achieved Rank D in Online Mode.
Won 25 or more battles in Online Mode.
KO'ed every character in Arcade Mode using Mature.
KO'ed every character in Arcade Mode using Goro Daimon.
Achieved Rank E in Online Mode.
Competed in 100 or more battles in Online Mode.
KO'ed every character in Arcade Mode using Ryo Sakazaki.
KO'ed every character in Arcade Mode using Clark Still.
KO'ed every character in Arcade Mode using Duo Lon.
KO'ed every character in Arcade Mode using Sie Kensou.
KO'ed every character in Arcade Mode using Ralf Jones.
KO'ed every character in Arcade Mode using Terry Bogard.
Competed in 30 or more battles in Online Mode.
Competed in 10 or more battles in Online Mode.
Won 5 or more battles in Online Mode.
KO'ed every character in Arcade Mode using Raiden.
KO'ed every character in Arcade Mode using Athena Asamiya.
KO'ed every character in Arcade Mode using Benimaru Nikaido.
KO'ed every character in Arcade Mode using Shen Woo.
KO'ed every character in Arcade Mode using Iori Yagami.
KO'ed every character in Arcade Mode using Robert Garcia.
KO'ed every character in Arcade Mode using Kim.
KO'ed every character in Arcade Mode using Andy Bogard.
KO'ed every character in Arcade Mode using Joe Higashi.
Inflicted critical counter-attack damage at least 10 times in Versus Mode or Online Mode.
KO'ed every character in Arcade Mode using Ash Crimson.
Cleared Arcade Mode in under 3 minutes and 30 seconds.
KO'ed every character in Arcade Mode using Kyo Kusanagi.
KO'ed every character in Arcade Mode using Leona Heidern.
Cleared Arcade Mode within 4 minutes.
Executed a counter-attack at least 50 times in Versus Mode or Online Mode.
Executed a counter-attack at least 30 times in Versus Mode or Online Mode.
Executed a counter-attack at least 10 times in Versus Mode or Online Mode.
Achieved Rank F in Online Mode.
Cleared Arcade Mode within 6 minutes.
Cleared Arcade Mode within 8 minutes.
Cleared Arcade Mode within 10 minutes.
Cleared Arcade Mode without using CONTINUE.