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