Here is the full list of all 19 Gravitar: Recharged achievements.
Kill an enemy by leading it to the laser cannon
Exit the reactor level with less than 1s before the reactor explodes
Destroy 150 asteroids in the solar system
Complete the first solar system without losing a life
Crash into the star without any fuel
Complete all singleplayer missions
Complete all 6 types of planets
Complete all 6 planets in 4 solar systems
Use all power-ups
Reach 10000 score in Arcade
Kill 25 enemies while under the effectTotal enemy kills while under the effect of Overload of Overload.
Kill 25 enemies with a Railgun shot
Kill 200 enemies with a Spreadshot
Kill 125 enemies with Homing Missiles
Kill 50 enemies disabled by the EMP
Shoot down 300 UFOs
Destroy 150 basic turrets
Push 40 buttons
Retrieve 100 rescue pods