Imu clearly massively outclasses Luffy and is Top 1 all time. Shanks said his power is immeasurable and taking him out rn would also waste all the Gorosei and God’s Knights as well deflate the inevitable Void Century flashback. Luffy beating him this arc would kill all stakes and tension for the rest of the story. However on the other hand Imu winning but somehow not killing Luffy might be just as bad. Kaido, CP9, Aokiji, and Crocodile, all either were too arrogant and lazy to finish Luffy off, naively thought they could break Luffy’s will and turn him into their underling, or weren’t actually hostile to Luffy. Imu has already said he’s let go of his arrogance before descending. As seen by what he said after Harald died, he doesn’t want to take Luffy as subordinate, and he hates him.
