You need to get ~3000 powerups in ONE run. This is approximately 15 planets.
It's almost impossible to do it at late stages of the game because of too big difficulty and rare planets spawn rate.
First of all you need to Reset your profile. The best way to do it, without losing game progress is to move save file (record.dat) from game directory (\Steam\steamapps\common\RBS\) to another place, and just put it back after you got this achievement.
It look like difficult of the game is depending on average progress. So the first 20 - 40 of runs you should killing yourself immediately. Then you could make few runs to collect stars. You need to upgrade RADIOSHIELD on 50%-75%, and add one point to CLAYMORE to deal with fog event.
Start new run when all preparations are done. DON'T shoot anything, and just avoid enemies. Try to have as less score as possible. If you doing all right, you won't get bosses for all the run, but you will getting planets!
The rest is a matter of time.