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