Here is the full list of all 12 Outland achievements.
Complete any Co-op Challenge Room (General)
Collect 1,000,000 Doubloons (Single Player only)
Complete the full game (Individual)
Collect all Marks of the Gods (Single Player only)
Destroy six enemies with one Beam Shot (Individual)
Collect 10 Marks of the Gods (Single Player only)
Smack a bomb so that kills two or more enemies (Individual)
Destroy an enemy using a Kamikazer (General)
Kill 20 enemies in a row with only 1 health left (Individual)
Complete any Arcade Chapter below the target time (General)
Defeat any boss without taking damage (General)
Destroy a Spider using spikes (General)