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