Here is the full list of all 27 Little Busters! English Edition achievements.
Complete the School Revolution ending
Activate Saya's ecstasy mode
Defeat Mask the Saito and obtain 1st place in the battle rankings
Defeat the Unknown Lifeform as Rin
Obtain a high score in the catering minigame
Complete Yuiko Kurugaya's true ending
Complete Kudryavka Noumi's alternate ending
Complete the Final Muscles ending
Reign victorious in the baseball match
Complete Kanata Futaki's scenario
Complete all heroines' scenario
Complete Sasami Sasasegawa's scenario
Observe the Science Club Corps backing Mio up in the battle rankings
Complete Saya Tokido's scenario
Complete the main scenario as Rin's lover
Complete the main scenario
Complete Rin Natsume's scenario for the second time
Complete Mio Nishizono's scenario
Complete Yuiko Kurugaya's scenario
Complete Kudryavka Noumi's scenario
Complete Haruka Saigusa's scenario
Complete Rin Natsume's scenario
Take a commemorative Little Busters group photo
Obtain 1st place in the battle rankings
Witness Mask the Saito's entrance into the battle rankings
Complete Komari Kamikita's scenario
Watch the opening movie