i would have had this in my guide, but i had to delete it because it didnt post.
You have to do this in co-op. 1 guy go to one side of the enemy, other guy go to other side. Then, 1 guy press SQUARE, for those “uppercut” and “Roundhouse” things (physical attacks) and then the enemy will go to other guy, and they will have to press SQUARE. Do this a few times, and you will get it.
A very easy way to do this is by putting the game difficulty to veteran and playing through chapter 2-1 until you can across the big man majini. Once you find one take all of Shevas weapons away and shoot him in the head until you can start the combo, sheva will do her part and then you can put the final hit in.