Mastered UI Goku vs perm-fusion Kefla
Lets say Kefla keeps with the original concept of potera fusion, and becomes a regular sparring partner for Goku. She carries over all her LSSJ amps to the next round.
How long can UI Goku take her down before he gets overwhelmed.
Say they spar about ten times a day, every day for an entire year. Giving Goku just enough time to rest between UI powerups.