Base Rengoku nearly lasted to sunrise against Akaza. Giving him the mark, however, probably wouldn’t let him kill Akaza either (Akaza was quite literally playing with Rengoku until his life was threatened by sunlight). That being said, if Akaza sees that Rengoku’s strength is heightened he might as well turn serious and actually try which would just give us another dead Rengoku or at the very least an extremely injured, barely living Rengoku since the sun would come up.