To be clear, that legacy was already rock solid before 2018. He was already an Olympian and a two-time defending UFC champion. He was one of the most respected men in combat sports -- a guy who was willing to switch weight classes midway through his career for the sake of his friendship with a heavyweight teammate.
But part of his legacy also was "second place." Great, but not the greatest. As accomplished as he was in wrestling, Cormier never beat Cael Sanderson when they met in college. He never medaled in the Olympics. And he never beat Jon Jones for the light heavyweight championship.
Coming into this year, Cormier admits he was struggling to come to terms with that legacy. As he exits 2018, however, that legacy has changed.
"The universe is crazy," Cormier told ESPN. "Just as you start to accept, 'Maybe I'm the guy that was second' ... The reality is my career was good enough to reach unbelievable heights ... But I was never the guy that stood at the very top. I didn't get that Olympic champion moment. I was at a point where, 'This has to be good enough for me.'
"When I came into this year, I was like, 'I'm just going to live this thing for what it is: a chance to compete and see where the chips lie.'"
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With Jones out of competition after a failed drug test, Cormier distanced himself from that rivalry in ways many of us wouldn't have thought possible in 2017.
He dominated both Volkan Oezdemir and Derrick Lewis with early finishes. But the defining moment came in July, when Cormier captured the heavyweight championship by knocking out Stipe Miočič, the most dominant heavyweight champ in UFC history.
"Everything wasn't pointing to, 'I have to get back to the Jones fight and make that right,'" Cormier said.
"I took on too much pressure in that rivalry, trying to put him in place. The reality is, he put himself in place with the indiscretions and bad things he did. Even after Jones was reinstated [in October], it wasn't about him. It was my story. It's crazy how everything changes so fast."