The Evil Eye Achievement
The Evil Eye15
Knock out 1,000 Evil Minions!
The earliest you see evil minions is level 50. Once you get there, you can start grinding this out as you play.
The Mega Minion power-up can help tremendously with this. The more you level up this power-up, the longer the power-up lasts, which in turn, gives you more time to knock out the minions.