King of Sleep wrote:For Two Cannot Exist Together, you don't need another person. Just use Yoshimitsu against the CPU. Knock the opponent's health down to a low level and also let him/her hurt you a lot then run at the opponent and hit X+B when you're really close. If the opponent doesn't sidestep or counter your attack, you'll stab yourself through the midsection and also get your opponent at the same time for a double KO. You and your opponent don't have to have super low health, 25% and maybe even 35% will do just fine.I did notice that I got a double KO in Arcade and did not get this achievement, then later I got another double KO using this trick and the achievement unlocked. I am not dead sure but I think you have to do the double KO in the first round when you and your opponent have not won any rounds, or maybe you just have to do it when you and your opponent have won equal numbers of rounds.