Here is the full list of all 20 Platformines achievements.
Finish the game in Ironman mode
Finish the game in Hardcore mode
Fall to your death
Open all the big red chests
Activate 300 portals
Kill 500 enemies with the Pistol
Kill 500 enemies with the Machinegun
Finish the game in Normal mode
Equip the Creeper hat
Accumulate 500.000$ selling gems
Kill 500 enemies with the Bazooka
Find a diamond in the mines
Hit beholders (flying eyes) 20 times in a row without losing any bullet
Accumulate 250.000$ selling metals
Kill 2000 enemies
Accumulate 1.000.000$
Accumulate 250.000$ selling weapons
Kill 10 human characters within a minute
Kill 500 enemies with the Shotgun
Hit human character 20 times with bullets without taking any damage