Here is the full list of all 31 Square Heroes achievements.
Complete 100 games
Earn all other Achievements
Host 20 Internet games with remote players
Kill opponent with Nuke Bag
Host an Internet game with remote players
Kill with Laser and Machine in round
Kill with Proximity Mine
Kill with Cross-bow and Harpoon
Score Devastation
Kill with Fire! (Flamethrower and Molotov)
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Score Mega Kill
Replenish 150% Team ammo
Re-gen 200% Team health
Complete 5 LAN games
Win 5 games in a row
Win without anyone else scoring (3+ players)
Win DM using only Explosives (3+ players)
Score Multi Kill
Survive Survival!
Score three Kill Streaks in a match
Score two Kill Streaks in a match
Win team game 4+ players with 75% or more of team score
Capture Gnome opponent almost captured
Capture 15 Gnomes
Play entire round without dying (3+ players)
Re-gen your health twice over
Score Double Kill
Score a Kill Streak
Score First Kill
Complete Tutorial