This can be unlocked with two human players and two AI players. Create a Team Deathmatch game with one human on each side. For the person earning the achievement, you can let your AI partner do much of the heavy lifting while you simply support him and play defense if you get attacked by the enemy AI. The human player losing simply needs to pass every turn, or can actively obstruct his partner by haunting shrines and rice patties but never attacking. If your AI partner survives, you will also unlock "Team Player" if you have not done so already.
If you do this in a Skulls Anywhere game mode (as opposed to Skulls Online on the XBLA) you can load up the final turn on all three devices simultaneously and unlock the achievement without having to play three separate games. Note that if you let the AI take the final move and the game ends without having loaded it on the other devices, the game disappears and you will have to start a new one to unlock it on the other devices.
You do not need to survive in order to unlock this achievement. As long as your team wins, you will satisfy the conditions for the achievement regardless of the status of your general.