Hawken

Works in Multiplayer only!

It's a quite simple achievement, you will get it eventually.
Just look which enemy mech has the lowest health and tries to steal away (to repair).
You can see a mech is repairing when he is crouched and a drone flies over him.
Look in corners or other hiding spots where you would go to repair.

I got it while playing the energy unit collecting mode (with the spaceship attacking the base)
When both teams are defending the FLAK gun and you damage an enemy mech,
they usually won't run far away from the flak to hide/repair, just sneak around every corner
and look.

A Friend and I got this easy by first selecting a low population server like South America. (From main menu select play then on the top right select the server South America) Then we picked death match. It was only us in the match.

Get your friend's mech low, have them repair, then kill them.

Deathmatch is the best game mode. You need 10 people to completely fill a lobby. Then select either Asia or Oceania servers. (They barely have any people)

Then scroll all the way down on the server browser until you get to DEATHMATCH. Also from completing this today we think that BUNKER and FACILITY are the best maps, since they are the smallest. Then call out the name of the server so everyone can join.

The rest is pretty self-explanatory: Get 1 kill while the enemy is repairing.

Tips to speed this up: Let one person get all the kills we were averaging 70+ kills for one person in 7 minutes. Also shoot yourself twice with the tow rocket so that the person killing can kill you faster.

The Mech called the Berserker has the least amount of health. Shooting two rockets won't kill you. (You also can buy this Mech to unlock the Reaper and Marauder faster which you need for two separate achievements)