This achievement can be done with a friend in two-player "VIP" matches, as hardly anybody seems to play the "VIP" games.
Start a ranked match for two players on a specific map of your choice (do not pick Random), and set the game mode to "VIP". Your friend needs to search a Custom Match for the map of your choosing, with the "VIP" mode in Ranked. Then your friend needs to kill himself. Do this elevent times for the achievement. Do not click Ready in your "VIP" lobby until you see your friend in the lobby with you, as you may come across a random player, and may lose your winning streak should you play that random player. Whilst going for this achievement, both yourself and your friend will also get Clearly Important.