Hyperdimension Neptunia Mk2

The combo hit counter increases everytime you hit an enemy, and it keeps increasing until either you do something other than attack (like healing), or an enemy takes its turn. Using standby does not break the combo. Hitting multiple enemies at once increases your combo even quicker. A good fight to attempt this is the Ram and Rom in Chapter 3, in New Game+, though any fight with multiple boss characters works well. Have all four characters surround the twins, and keep pressing to standby. Once you have accumulated 2 turns of AP for all four characters, unleash all of your attacks. Be sure that your attacks hit both twins whenever possible. I managed to get a 118 hit combo in this fight.

Some other good fights to try is the Level A fake CPU fights in the coliseum (except for Green Heart), since there are multiple enemies with high HP that even works with level 99 characters.