Have you noticed that sometimes when you throw people or combo people, a little substitution mini-game occurs? This is when you throw or hit someone in a particular direction, and then continue pressing the attack button in the direction you threw them. Each time the substitution mini-game takes place, it counts as an additional hit. You do not actually have to win the substitution thing in order for it to count as an additional hit, but it definitely helps you win the fight if you do.
you need to start it to win. if you only need three than you have no problem with finishing them. if you need six than it is wiser to only start them and then just let them win it.
Yeah, especially when your character is highly upgraded, if you have to do six, just start them and let them finish it, or else you may kill them before you get the number required.