If playing in Single Player mode, make sure that Sheva has no weapons. By doing this, she will not shoot when you do not want her to. You will also need a flash grenade. If you do not have one, go to Chapter 4-1 and get it at the beginning. Quit the level and save your equipment, then go to Chapter 6-1, "Ship Deck". Eliminate all the enemies that are triggered when you drop down. Continue past the tower and drop down near the containers. Go to the stairs to the right, which will trigger a couple Adjule (dogs). Kill them quickly since there are two Majini with melee batons coming down the stairs. Once these enemies are gone, continue forward until you hear a Big Man Majini yell at you. Quickly pull back so you do not trigger any other enemies, then lure the big Man Majini to where you just fought the Adjule. Use your flash grenade to stun him, then run up to him and use the contextual action to do a melee attack. Sheva will do another attack, which you will follow up immediately with another contextual action attack. This will dispose of the Big Man Majini and grant you the achievement.