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 any Arcade Chapter below the target time (General)
Defeat any boss without taking damage (General)
Complete the full game (Individual)
Collect all Marks of the Gods (Single Player only)
Smack a bomb so that kills two or more enemies (Individual)
Destroy six enemies with one Beam Shot (Individual)
Kill 20 enemies in a row with only 1 health left (Individual)
Destroy a Spider using spikes (General)
Destroy an enemy using a Kamikazer (General)
Collect 10 Marks of the Gods (Single Player only)