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