Unlockable Characters and pilots - Beat these peoples story mode on any difficulty.

Char Aznable and Char's Gelgoog Complete Amuro Ray's Story Mode On Any Difficulty In Offical Mode
Char's Zaku II Complete Char Aznable's Story Mode On Any Difficulty In Offical Mode

Elpe Ple and Qubeley Mk-II (Black) Complete Both Judau Ashita & Domon

Kasshu's Story Modes On Any Difficulty

Emma Sheen Complete Both Char Aznable & Rolan Cehack's Story Modes On Any Difficulty

Haman Karn, Judau Ashita, Qubeley Gundam, and Gundam ZZ Complete Judau Ashita's Story Mode On Any Difficulty In Offical Mode
Hyaku Shiki Complete Mission 4 Of Char Aznable's Offical Mode On Any Difficulty

Jerid Messa and Gundam Mk-II (Black) Complete Both Kamille Bidan & Heero Yuy's Story Modes On Any Difficulty

Master Gundam/Master Asia Beat Domon/Burning Gundam's Story mood on any difficulty.
Milliardo Peacecraft and Gundam Epyon Complete Heero Yuy's Story Mode On Any Difficulty In Original Mode
Musha Gundam Complete Story Mode For Amuro Ray, Kamille Bidan, Judau Ashita, Domon Kasshu, Heero Yuy, and Rolan Cehack On Any Difficulty

Paptimus Scirocco and The O Complete Kamille Bidan's Story Mode On Any Difficulty In Offical Mode
Ple Two Complete Elpe Ple's Story Mode On Any Difficulty In Original Mode

Qubeley Mk-II (Red) Complete Both Elpe Ple & Rolan Cehack's Story Modes On Any Difficulty

Roux Louka Complete Both Judau Ashita & Haman Karn's Story Modes On Any Difficulty

Complete each achievement to get the allotted gamerscore.

Unlockables

100 TOTAL MISSIONS Complete (75) Complete 100 or more TOTAL MISSIONS. Data must be saved to unlock this achievement.
50 TOTAL MISSIONS Complete (50) Complete 50 or more TOTAL MISSIONS. Data must be saved to unlock this achievement.
All Skills Acquired (100) Acquire all skills for at least 1 characters. Data must be saved to unlock this achievement.
Character Gallery Complete (75) Unlock all characters in the Character Gallery. Data must be saved to unlock this achievement.
Mobile Suit Gallery Complete (75) Unlock all Mobile Suits in the Mobile Suit Gallery. Data must be saved to unlock this achievement.
Mobile Suit Level MAX (75) Attain a Mobile Suit Level of 10 for at least 1 MS. Data must be saved to unlock this achievement.
OFFICIAL MODE: 1 Character (25) Clear OFFICIAL MODE using 1 or more characters. Data must be saved to unlock this achievement.
OFFICIAL MODE: 3 Characters (50) Clear OFFICIAL MODE using 3 or more characters. Data must be saved to unlock this achievement.
OFFICIAL MODE: All Characters (75) Clear OFFICIAL MODE using all characters. Data must be saved to unlock this achievement.
ORIGINAL MODE: 1 Character (25) Clear ORIGINAL MODE using 1 or more characters. Data must be saved to unlock this achievement.
ORIGINAL MODE: 8 Characters (75) Clear ORIGINAL MODE using 8 or more characters. Data must be saved to unlock this achievement.
ORIGINAL MODE: All Characters (100) Clear ORIGINAL MODE using all characters. Data must be saved to unlock this achievement.
Pilot Level MAX (75) Attain a Pilot Level of 30 for at least 1 character. Data must be saved to unlock this achievement.
TOTAL SHOT DOWN 100000 (75) Shoot down 100000 total enemies. Data must be saved to unlock this achievement.
TOTAL SHOT DOWN 50000 (50) Shoot down 50000 total enemies. Data must be saved to unlock this achievement.