Here is the full list of all 31 Initial2: New Stage achievements worth 1,000 gamerscore.
Game Begins
Beat '(Fake)Scientia Emperor-Rex-the Liberator' at any mode
Beat General Nihil at any mode
Beat General Kyuya at any mode
Beat General Ryuzaki at any mode
Beat General Motalia at any mode
Clear Story Mode or Challenge Mode
Clear the Limit Mode
Beat Doom Machine · VE Ⅱ at any mode
Beat Energetic Aberration-Old King Armour at any mode
Beat the Ace Drillmaster-Sophia at any mode
Beat Operator-Viola at any mode
Beat Blood-Starved Mortalia at any mode
Beat The Forsaken - Dennis at any mode
Beat Veritas at any mode
Beat Replicant Ryuzaki at any mode
Unlock weapon Greatsword-Shiver
Unlock weapon Fists-Wild
Unlock weapon Bow-Falcon
Own 1 ESP chip
Own all ESP chips
Own 1 E.M.C skill
Own 4 E.M.C skills
Own all E.M.C skills
First time to use Executioner Skill
First time to rescue teammate
First time talk to NPC
First time to use skill of recovering HP
Unlock all information of enemies
Unlock all information of main characters
Beat one BOSS in BOSS Challenge Mode by S score