Here is the full list of all 16 Chopper To Hell achievements.
COMPLETE LEVEL 01 ON EASY DIFFICULTY
COMPLETE ALL LEVELS ON EASY DIFFICULTY
COMPLETE LEVEL 02 ON MEDIUM DIFFICULTY
COMPLETE ALL LEVELS ON MEDIUM DIFFICULTY
COMPLETE LEVEL 03 ON HARD DIFFICULTY
COMPLETE ALL LEVELS ON HARD DIFFICULTY
SURVIVE LEVEL 01 FOR ONE MINUTE ON NIGHTMARE DIFFICULTY
SURVIVED LEVEL 04 FOR ONE MINUTE ON NIGHTMARE DIFFICULTY
FIRE 10000 BULLETS
FIRE 100000 BULLETS
FIRE 1000000 BULLETS
KILLED 200 SPIDERS IN TOTAL
KILLED 2000 SPIDERS IN TOTAL
KILLED 20000 SPIDERS IN TOTAL
KILLED 200000 SPIDERS IN TOTAL
KILL SPIDERS IN A LEVEL USING ONLY FLAME THROWER