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)
Complete the full game (Individual)
Collect all Marks of the Gods (Single Player only)
Destroy six enemies with one Beam Shot (Individual)
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)
Destroy an enemy using a Kamikazer (General)
Defeat any boss without taking damage (General)
Complete any Arcade Chapter below the target time (General)
Destroy a Spider using spikes (General)