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could have been solved in 15 minutes if the 2 antagonists would just talk to each other, and that's actually what the movie ends up doing in the end. Wikipedia sums it up as "Afterward, Donnie reconciles with Dame, with both men admitting it was not the other's fault." and that's pretty much what could have happened straight from the start... but there wouldn't be any movie if it did, right ? So we're getting 2 hours of this rich famous guy FINALLY understanding "hum, maybe I should just talk to him". But only after beating the hell out of him as a "sport", because that's what tough men do, I guess ?
Indeed, the earlier scenes were the best, because of how much backstory and hesitations it was giving to its main protagonist, and then, well, there was still 100 minutes to sit through, and those ended up being, in the end, quite formulaic.
What Creed III has for it though is a certain visual flair, and Majors effectively menacing presence, though the movie under-uses it (and I suppose we might not see much more of Majors for the moment if a sequel was to get greenlit very quickly).