In order to get all of the achievements, you simply have to lunch the game and notice a countdown on the top right corner. It's a 30 minute count.

When the 30 minutes are up, you simply press there. It will trigger 500 achievements and the countdown resets.

Repeat until you get all of the achievements.

You can minimize the game and browse the Web while you wait for the time to pass, you don't need to be staring at it.

In case the first achievement doesn't drop, close the game, go to

steam \ steamapps \ common \ NeoBoom2 \ NeoBoom2 \ Saved \ SaveGames
and Delete Level.sav

After that re-open the game and try again. This should fix your problem.

<3