Here is the full list of all 27 Sky Mercenaries achievements.
Finish a mission stage in Hardcore mode
Share a unique created stage
Create a new 100+ objects stage
Download and play a user created stage
Become a Defense Ace - Unlock all John Hawk Skills
Install all Ship upgrades up to lvl 25
Become a Air Sniper - Unlock all Lea Striker Skills
Complete all Stages on all Planets
Kill 10000+ Enemies
Become a Drone Master - Unlock all Bill Riddim Skills
Test 10+ different Ship, Pilot, Drone and Upgrade Combinations
Upgrade your Ship 10+ times
Unlock first DroneMaster Player Skill
Play one of your Ships to ShipLevel 10+
Collect 100 000+ overall Credits
Unlock first Defense Ace Player Skill
Finish a Stage at 150% Difficulty or harder
Absorb 200+ Bullets in one Stage
Collect 1000 Powerups
Visit all Hangar Areas
Unlock first Air Sniper Player Skill
Kill 1000+ Enemies
Complete all Earth C-1 Stages
Finish the first Stage
Reach Ship Level 2
Change Firemodes over 20+ times in one Stage
Change Firemode to incomming Bullet Color