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 any Arcade Chapter below the target time (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)
Defeat any boss without taking damage (General)
Destroy an enemy using a Kamikazer (General)
Kill 20 enemies in a row with only 1 health left (Individual)
Destroy a Spider using spikes (General)