Does this achievement have to be unlocked in nightmare mode?

New Mode "Boss Mode", this mode is unlocked by defeating each boss once during any of the other modes, if you already have the laser weapon unlocked you'll already have it enabled after the update. During this mode we've made some tweaks to Bos...

I'm fairly certain I've encountered and beaten every boss. I've reached >1,000,000 poins in casual, 900,000 points in normal and 200,000 in hardcore. I recognize every boss in the trading cards. I tried resetting save data and doing it again but both times Pew Pew Pew was the only achievement that didn't unlock....

I just bought the game and I can play just fine... except for the obvious line glitches that spaz everywhere all the time... is there a way to fix this?

http://steamcommunity.com/sharedfiles/filedetails/?id=597181867 This is what happen when you survive for to long. Obscene ammount of fire power + 360° invisble shot. We're going supernova over here.