Here is the full list of all 21 Cybarian: The Time Traveling Warrior achievements worth 1,000 gamerscore.
Reach the 3rd boss
Defeat the 2nd boss
Reach the 2nd boss
Defeat a cyborg-looking enemy
Defeat a fat enemy
Play a slot game
Defeat the 1st boss
Buy 5 hearts
Reach the 1st boss
Reach the 1st boss in Hard Difficulty
Buy 3 hearts
Destroy a Laser Eye
Defeat a bomb launcher enemy
Buy 1 heart
Get 40 coins
Defeat a rifle enemy
Get 20 coins
Get a coin
Defeat a bandana-enemy
Hit a homless guy
Complete a full combo