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