I am sure there are plenty of ways to is this, but I did it with Arakune.
Go into Vs mode. Pick Arakune and anyone else.
Get Arakune up to full super meter by doing damage to him and instant blocking. You don't want to player 2 on low health because you need the combo to land.
Once Arakune has full meter go near the opponent, activate Overdrive and do his super that is down, down/forward, forward twice and C (circle button). Arakune transforms into a flower and shoots a laser above his head. The laser does a ton of hits. Once it ends quickly do the super again before the opponent can fall tok far. If done correctly the laser will hit the opponent and you will end with a 100+ hit combo.