Syndicate

This CAN be done solo

On the Co-op mission Scandinavia (Private Match-Solo) fight through until you reach the UGV. Once you activate it fight off enemies until the sergeants start to appear. One should spawn with an Electron Mace. Once you see him simply just hide and it will attack your UGV. Shoot and kill him simple as that.

Found this out by accident so i can confirm it works this is how i got the achievement

edit: Also thanks to Jodmeister he has confirmed that if you are being attacked by an electron mace and kill the attacker while still being damaged by the mace, but not stunned, the achievement should pop.

Straightforward, once you see an electron mace. I first saw one on co-op mission 4. The Electron Mace fires a beam (looks kind of like lightning) which stuns and locks up one of your teammates. Kill whoever's holding it (usually a Sergeant) and this pops up right away.

These are most common in the Aspari missions, so look for Electron Mace enemies in Colorado, China, and Scandinavia (4-6). Chances are you're going to get maced more than enough in China, especially in the tunnels right before the final boss fight, so that's a good place to try and get this.

They appear on all difficulty levels, so you can get this on Normal, Hard, or Expert. Easiest on Normal, if only because the enemies holding the electron mace die the fastest, but not that much more difficult on Hard/Expert.