Cristiano Ronaldo and Lionel Messi, Roger Federer and Rafa Nadal, Muhammad Ali and Joe Frazier, Jack Nicklaus and Arnold Palmer.
All great rivalries that defined their sports' in their eras, and athletes who each helped elevate the other to greatness.
In the world of CrossFit, there's Mat Fraser and Mat Fraser. Alone, peerless at the top of his sport, competing with and for his legacy, pushed by his own motivation to continue to grow.
At last year's CrossFit Games, Fraser won six of the 13 events and finished 216 points clear of his nearest rival, Canada's Brent Fikowski. With a maximum of 100 points available per event, this margin of victory represented the most dominant performance in CrossFit Games history.
What's even more remarkable is that Fraser's success came while he was injured. Stretching after the first day's competition, Fraser felt something tear in his knee, and thought his Games were over.
"It was pretty scary. It was loud," Fraser tells CNN Sport, casually describing what could have been the end to an entire season of competition. "If I lifted my leg up to the side my knee bent the wrong way like it just drooped and I was like, 'Oh, that's not good.'"
'Odds are I'll need surgery'
Knowing the risk that the on-site doctor might not allow him to compete had he reported his injury, Fraser decided to keep it to himself and roll the dice in the hope he wouldn't do more damage.
"I didn't know what tore," he says. "I didn't know how bad it was, but I knew it was bad. Odds are I'll need surgery, so if it blows out, it blows out. I didn't want any of the sharks smelling the blood in the water, So I just put on my face and not let anyone know I was hurt."
Fortunately for Fraser, the damage was not enough to severely affect his ability to compete, and after a string of dominant performances, the defending champion headed into the final event knowing the title would once again be his.
Throughout the four days of competition, Fraser kept his head down, workmanlike, avoiding looking too closely at the scoreboard or listening too closely to the crowd. But once he knew he could no longer be caught, he afforded himself a brief moment, stopping halfway through the final event to pause and take in the experience.
"[His agent Matt] O'Keefe was telling me, 'When you're 40, you want to have a handful of memories that will be with you for the rest of your life. You're making these moments now. Soak this in,''' Fraser tearfully recounts.
"So I hit the minimum work acquirement and was like, 'OK this is the moment to look around and take it in,' and looking around I was like 'Oh my God. So many people. This is what the whole year has been about. This is it.'"
'I didn't think I was capable of that'
Fraser's emotional reaction to this moment is not something many have seen. More private than many other CrossFit Games athletes, Fraser rarely posts on social media and enjoys spending much of his time at home with his girlfriend Sammy, riding his motorcycle and shooting guns.
His garage, where we sat for the interview, has more workout equipment than many gyms, allowing Fraser to train alone.
But things have changed. After the 2017 Games, Fraser and Sammy moved from Vermont to Cookeville, Tennessee to the same town as four-time CrossFit Games champion Rich Froning. Remarkably Fraser seems to be getting even fitter.
During the Open, the worldwide qualifying competition that takes place throughout February, Fraser topped the leaderboard by a margin more than four times as wide as his remarkable 2017 victory.
"I have a handful of workouts that I know what my score was a year ago," Fraser explains. "Wow. Like I didn't think I was capable of that."
Assuming he can stay healthy at this year's CrossFit Games, who knows what Fraser might be capable of?