Here is the full list of all 44 Secret Agent HD achievements.
Destroy 10 mecha-spiders
Complete all achievements.
Spend at least 60 seconds under the water
Collect every flag in the game
Finish Episode 4
Collect over $1000000 worth of bonus items
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Complete any level without killing any enemies
L10 without killing any enemies and with a perfect health.
Destroy crawler bot while in the air on medium or hard difficulty.
Collect 100 tombstones
Kill an enemy while wearing a jetpack
Hold 6 keys in your inventory at once
Finish Episode 3
Get maximum rapid fire
Kill 50 Ninja's
Catch 50 hidden coin bags
Finish Episode 2
Use the teleporter 50 times
Collect 25 toothbrushes
Stack two barrels, one on another
Disable laser grid 20 timesCHIEVEMENT_DESC_23_16
Destroy 10 tombstones
Finish any level in under 60 seconds
Finish 5 custom maps from the Workshop
Collect all island treasure.
Complete any episode without taking damage.
Complete any episode in one session without loading.
Complete any episode on hard mode.
Finish Episode 1
Finish any episode on HARD with 35 ammo or more
Collect All Magnifiying Glasses in any episode
Get confused and slowed down at the same time.
Life is better in the hot tub.
Finish a level with an extra key in your inventory.
Blow up enemy with a Dynamite
Collect SPY letters in wrong order
Finish any level
Finish any level with a perfect score
Collect all SPY letters in the right order
Die in water