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