Okay, first of all, this isn't technically a guide, as this is a super conditional achievement that requires a ridiculous amount of luck. You could just blow up walls and hope somebody is behind it, but that's incredibly rare, so here's my strategy on how to increase your odds of getting the breach charge kill.
I recommend playing in the bomb game mode, because the enemy team will have to be split up. You can set this in your preferences so you'll only play this mode. Then you basically have to clear out one entire bomb site of enemies, and hope that the other side is relatively untouched.
Once you've got this part out of the way (which isn't always easy), try to place a breach charge on the main barricaded door of where the untouched bomb location is. Once that is there, plant the defuser at the other bomb site.
Now the enemies that are at the untouched bomb site will be forced to go to where you are, and will most-likely be forced to use the main door that you've put a breach charge on. Watch under the door, and when you see feet get close enough to the door, blow it, and hope it does enough damage to kill.
Keep in mind, this isn't a guaranteed achievement. It's still stupid luck-based. This is just the way that I've found to narrow your odds of getting an enemy to your breach charge by forcing the enemy's hand.
Let's hope this link works. This is the video of me actually getting the achievement. You can see that our team had A planted, forcing the enemies in B to have to move out to us. So I just placed my charge on the door, and he came right to me.
Hope it helps, and good luck!