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