if you go by overall skillset, athletic ability, Khabib is the least talented. On Mental aspects, he is goat level though.
You can question that Usman is more talented than Umar, that's totally fine, I am simply relaying what his coaches that see him daily have been repeating for years now. Usman is a better athlete than Umar, just visually, also as a traditional martial artist myself, I can tell you that he is more fluid as a traditional martial artist than Umar too. He is definitely the more talented fighter in my eyes, however talent is paradoxical and can be a detriment sometimes, and is not always the stamp for success.