Two Controller Method:UPDATE: People in the comments are saying that they were also able to do this against the CPU, just that it requires a little more effort because the CPU fights back, so this is also an option.
The extra hit is extremely low powered so you really need your opponent to be as low as they can be in health for you to beat them with it. Luckily I found a combo that puts the opponent as low as their health will go without them being at zero.
Head into free battle mode and hit
on your second controller to put the match into player vs player mode.
Select Naruto as the character you will be playing as (not sure of other characters will work, but Naruto’s throw works for our purposes because his throw will put your opponent at your feet.)
Hit
on the character select screen with Player 1, Put the Handicap completely in your favor.
When the match starts, hit the opponent once with
then Throw with
+
, When the opponent is down hit
next to them to perform an extra hit.
For the rest of the match keep throwing until your opponent has 1% health, then perform another extra hit (
).
If you followed the moves in the order I listed the opponent should be defeated with the last extra hit.
Here is a video of me performing moves that I listed in case anyone needs a visual aid: