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)
Complete any Arcade Chapter below the target time (General)
Defeat any boss without taking damage (General)
Collect all Marks of the Gods (Single Player only)
Kill 20 enemies in a row with only 1 health left (Individual)
Destroy six enemies with one Beam Shot (Individual)
Collect 10 Marks of the Gods (Single Player only)
Destroy a Spider using spikes (General)
Destroy an enemy using a Kamikazer (General)
Smack a bomb so that kills two or more enemies (Individual)