Kane & Lynch: Dead Men

To boost this, simply hold your grenade (right bumper, RB) and do not let go. Have someone kill you and then stand on your corpse (better if they look for the actual grenade) because the grenade you held will fall primed as you die.

As long as they get killed from that grenade you were holding, it counts as a personal revenge kill.

This solution will give a player 1 traitor kill and 1 personal revenge kill per round. (this is similar to Shadow Enz solution)
4 players
3 rounds
Hot Coffee(first map on host screen and also has flat ground so the grenade wont roll unlike walk in the park)
Player 1 kills player 2.
Player 3 kills player 1
Player 3 holds a grenade (carefull not to throw it)
Player 4 kills player 3 and stands over the grenade
Doing this for one person (Player 3) for a full session will get them 3 traitor kills and 3 personal revenge kills.
Just switch who is Player 3 each session

Solution by MarkLaing07 (With credit to Shadow Enz too)

This achievement can be hard to get because of the lack of people playing nowdays. An easy way to boost this with a friend is to set the game to 5 rounds and 4 players, find a corner stand in it and have your friend stand close. Drop a grenade at your friends feet and then have your friend kill you before the grenade goes off (2 headshots up close) then just stand still to get revenge killed by your grenade. Respawn as security, kill or help the other mercs to finish the round quick and then repeat. Make sure that when you go for the personal revenge kill that your friend is not already a traitor otherwise it will only count as a traitor kill.