No idea. I thought stamina and ki would prevent infinites to begin with, but what do I know.
You might not be able to get a true "infinite" but in PQs and story quests you can chain combos high enough to hit "Z" hits (100+) which will kill large numbers of PQ and Story bosses. Often your combo gets broken by scripting (people going into their next form, new people showing up ,etc) before you can kill them.
Generally to do the infinite stuff you need Super Saiyan (or SSJ2) (maybe other races can do it too, I've only done it with Sayians) which makes your supers/ultimates not cost Ki for a limited time. Depending on your build that transformation time will often be enough to win if your Gear/Z-Soul work together to boost whatever move you're spamming (Death Ball is a popular choice).
EDIT: Beaten.
But note this isn't really effective in PvP. People are smart enough to dodge. NPCs aren't.