Here is the full list of all 12 Outland achievements.
Defeat any boss without taking damage (General)
Destroy a Spider using spikes (General)
Destroy an enemy using a Kamikazer (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)
Complete any Co-op Challenge Room (General)
Complete any Arcade Chapter below the target time (General)
Collect 10 Marks of the Gods (Single Player only)
Collect all Marks of the Gods (Single Player only)
Collect 1,000,000 Doubloons (Single Player only)
Complete the full game (Individual)