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There's a time in every fighter's career where he is pushed past the limits of where he has been tested before in order to prove he or she is truly great. For middleweights Israel Adesanya and Kelvin Gastelum, their respective defining moments just so happened to come in the same night, against one another in the same fight at UFC 236 in Atlanta

The result was 25 minutes of war and an instant classic inside State Farm Arena on April 13 for the interim 185-pound title. Adesanya, in the midst of a career-defining year, took home a unanimous decision on identical 48-46 scorecards. But the 30-year-old Nigerian won much more than a secondary trinket and a grotesquely swollen lip. 

Adesanya, who would go on to knock out champion Robert Whittaker six months later to unify titles, cemented himself as legitimately elite by the toughness he showed in repeatedly taking Gastelum's best shot only to plow forward in relentless pursuit. 

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As flashy as they come as a former kickboxing star with an audacious gift for gab, Adesanya still attracted many critics at this point in his rise who suspected he was more sizzle than steak. And it took an equally elite challenge by Gastelum to force "The Last Stylebender" to prove how great he could be. 

Gastelum, 28, had battled weight issues and inconsistency despite his many flashes of bright potential throughout his first six years in the UFC. This was the night he put it all together, however, by adding wrinkles to the way he sets up his booming left hand and establishing very early that he was there to go out on his shield in pursuit of the title opportunity he was robbed of when Whittaker pulled out 24 hours before their scheduled UFC 234 main event. 

It didn't take long to realize once Adesanya and Gastelum touched gloves that UFC fans were in for not just the best fight of 2019 but one of the most dramatic in MMA history. The two elite strikers, at the peak of their physical primes, inflicted damage on one another in a violent, seesaw affair. 

As good as the first three rounds were from the standpoint of tactical adjustments and brutality, the final two rounds were even better thanks to a series of hectic developments. Gastelum rocked Adesanya with a head kick in Round 4 but was unable to take him down and finish him. 

The final round was straight bananas. Both fighters endured nearly being submitted by deep chokes until Adesanya finally dropped Gastelum repeatedly in the final minute despite proving unable to force the stoppage. The combined levels of heart and stubbornness shown over the final five minutes were humbling. 

With so much at stake, neither fighter was willing to take the chance of having regret in pursuit of their title dreams. This was the kind of fight that births new fans and entraps them for life due to the almost inhumane levels of courage and brutality on display. 

2. Dustin Poirier UD5 Max Holloway (UFC 236)

How do you follow a fight as good as Adesanya-Gastelum? The quick answer is you don't. Yet somehow, someway this interim lightweight title bout that served as the main event in Atlanta came insanely close. This was the 28-year-old Holloway, already in possession of the UFC featherweight title, daring to be great by moving up to 155 pounds in hopes of nearing the immortality that comes with being a rare two-division champion. Holloway was so incredibly game in his attempt to do so by relentlessly absorbing damage and exploding forward as if winning this fight provided an opportunity to save his life. Yet what ultimately made it so good was that Poirier, at the age of 30, figured out on this night how to find the very best version of himself inside the Octagon that ever existed. Culminating a long journey of maturity and growth, Poirier was simply too big, too tough and too determined as outlasted Holloway in a high-speed classic. 

3. Vicente Luque TKO3 Bryan Barberena (UFC Phoenix)

They don't make them much more intense than this welterweight war that featured both fighters combining to land more than 300 strikes. Luque became the first fighter to stop the rugged Barberena as he broke open an even slugfest through two rounds and recorded the finish in the final seconds of Round 3 thanks to vicious knees to the face. Although Luque was able to secure the fight of the night bonus, he caught an earful from his fiancée thanks to the damage his face incurred just weeks out from their wedding. 

4. Stipe Miocic TKO4 Daniel Cormier (UFC 241)

The title rematch was a historic one in that both were looking to cement the title of greatest heavyweight in MMA history. Thirteen months after he was knocked out to lose his title, Miocic showed insane punch resistance by luring DC into a brawl and stopping him in dramatic fashion. Cormier fully abandoned the wrestling that saw him have his way with Miocic in the opening round and showed little respect for the punches that he walked through in order to stalk his opponent in search of a KO. Eventually, the toll caught up with him as Miocic targeted the body in Round 4 of a fatigued Cormier to finish him off. The Honda Center in Anaheim, California, proved once again to be a cursed venue for Cormier just two years after he was knocked out by Jon Jones in the same building in their rematch, which was later changed to a no contest. 

5. Kamaru Usman TKO5 Colby Covington (UFC 245)

Two of the best wrestlers in MMA today settled their grudge in this must-see welterweight title duel that ultimately saw zero takedowns attempted over five rounds. Instead, both men stood at short distance and let their hands go throughout in a cruel showcase of cardio, volume and toughness. Both fighters gave nearly as good as they received in this boxing match with four-ounce gloves. Finally, Usman broke Covington down enough to floor him twice in the final minute to produce the stoppage. Despite tasting defeat, Covington showed tremendous resolve in fighting through a broken jaw and swollen face for most of the fight. 

Honorable mentions: Mike Perry UD Alex Oliveira (UFC Fort Lauderdale, April 27), Jessica Andrade TKO2 Rose Namajunas (UFC 237, May 11), Paulo Costa UD Yoel Romero (UFC 241, Aug. 17), Jorge Masvidal TKO2 Darren Till (UFC London, March 16)