Brink

This achievement requires you to 'take down' an enemy with a Mine. Engineers are the only class capable of planting mines. By default, your mines can be selected with LEFT on the Directional Pad.

The description is a little misleading. The achievement wants you to incapacitate an enemy with a mine, not simply knock him to the floor. Nor do you have to outright kill him, simply incapacitate him to the point of requiring a medic (or his own syringe) to get back up.

Not all enemies will be incapacitated by a mine. For example, heavy-build, or even medium-build enemies if they have enough health buffs, can survive a direct mine detonation, and most enemies will survive the explosion if they are sprinting or SMARTing across it.

The two most reliable places to get a kill with your Mines are:
~~ In front of an objective you are defending. If an enemy Operative/Soldier is going to HAVE to stand next to it to complete their objective, you're near guaranteed to get a positive detonation. Also, often a planting/hacking enemy will have taken a little bit of fire on the way, and will be deprived of his health buffs and more likely to die.
~~ You could also try an obvious map chokepoint. If you're noticing a pattern - all the enemies crossing a particular bridge/entering a particular door, simply drop a mine in a likely location, and drop a few rounds into any approaching enemies.

If you'e having trouble online, don't forget that this can be gained playing solo. Simply select Campaign from the main menu, and set your settings to Solo play.

To place a mine you have to be an engineer. To select your mine,
press left on the D-pad and hold X until it is placed. Then just
wait for an unsuspecting enemy to walk onto it and be blown up. This can be done in campaign by yourself or online. It's not very hard but if you want it quick, I would recommend doing it in single player because it is less likely that the NPCs will notice the mine.
Cheers!

You must be an engineer to plant a mine.

I was able to get this in freeplay with the following settings:

From the main menu, start a private freeplay game.

Make sure the following options are chosen:
Game Mode: Objective
Play Mode: Solo
Map: Terminal

Under match settings:
Min/Max Team Size: 1

Once the game starts make sure you are security > Engineer then run to the objective, the AI will probably be there so kill them, plant the Mine as the AI comes back into the room, sit back and wait for him to set it off.

There is a little trick how i got it. On the map where you have to protect the cran from being hacked, you should plant the mine nearby the control field. If you see the enemy coming just let him get a few percents on the crane.

Then just keep shooting at him in short bursts, after a while he will run away and directly in the landmine and then you got the achievement.

You can also get this on the private match where you fight only one enemy :-) hope this helps