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