2021 proved to be a milestone year for the UFC as the world’s premier MMA organization continued to deliver stellar events every month. While many events in 2020 took place without a crowd due to COVID-19 restrictions, 2021 saw a comforting return to normalcy as fans were allowed back for certain numbered events.The year started off with a bang on Fight Island in Abu Dhabi as Conor McGregor returned to action to take on Dustin Poirier in a rematch at UFC 257 in January. The year ended with an incredible night of fights in Las Vegas at UFC 269: Oliveira vs. Poirier in December.Image courtesy of BT Sport on YouTubeFollowing the final numbered event of 2021, Dana White mentioned in the post-fight press conference that the company had shattered its previous annual pay-per-view revenue record for the calendar year.That being said, we ranked the five best events of the year based on the buzz going into the event, how stacked the fight cards were and the moments that they produced.Here are the five best events of 2021.#5. UFC 257: Poirier vs. McGregor 2 at Yas Island, Abu DhabiUFC@ufcOFFICIAL: Your Poirier-McGregor 2 poster has landed 💎🇮🇪[ #InAbuDhabi | @VisitAbuDhabi ]01:28 AM · Dec 24, 2020338815483OFFICIAL: Your Poirier-McGregor 2 poster has landed 💎🇮🇪[ #InAbuDhabi | @VisitAbuDhabi ] https://t.co/fbvMEO2RBEThe rematch between Irish superstar Conor McGregor and lightweight contender Dustin Poirier went down in Abu Dhabi. McGregor won the duo’s first bout back in 2014 with a first-round knockout. Going into the bout, Poirier was ranked No.5 in the featherweight division, while McGregor was at No.6.UFC@ufcRewind the clocks ⏳⏮ Look back on @DustinPoirier vs @TheNotoriousMMA from #UFC178 now. #UFC25711:15 PM · Nov 23, 2020164261762Rewind the clocks ⏳⏮ Look back on @DustinPoirier vs @TheNotoriousMMA from #UFC178 now. #UFC257 https://t.co/fgl3FuQ60lNotably, McGregor wasn't his usual antagonistic self in the build-up towards the fight. In fact, he was extremely courteous throughout fight week and was very complimentary of Poirier.McGregor was the favorite going into the bout, with many believing that Poirier would struggle with the power and accuracy of 'The Notorious'. Poirier repeatedly attacked McGregor's calf with powerful kicks, rendering the Irishman almost immobile in the second round.Poirier capitalized on his success with leg kicks and cornered McGregor into the fence with lethal hooks, one of which caught the latter flush on the chin. 'The Diamond' secured a TKO victory to level the series between the duo at 1-1.UFC@ufcOn the biggest stage, @DustinPoirier delivered 💎 What did you think of his performance?[ #UFC257 | #InAbuDhabi | @VisitAbuDhabi ]8:24 PM · Jan 24, 20214540410On the biggest stage, @DustinPoirier delivered 💎 What did you think of his performance?[ #UFC257 | #InAbuDhabi | @VisitAbuDhabi ] https://t.co/6G66PCn9bkThe co-main event saw Michael Chandler make a resounding statement in his promotional debut, securing a sensational TKO-victory over Dan Hooker. His incredible performance saw him break into the top 10 in the lightweight rankings.UFC@ufcA debut worthy of a title shot 🤯⚙️ @MikeChandlerMMA has his date with gold in Houston![ Join the Fight Club pre-sale: bit.ly/31zREVZ ]03:30 AM · Apr 1, 20214174433A debut worthy of a title shot 🤯⚙️ @MikeChandlerMMA has his date with gold in Houston![ Join the Fight Club pre-sale: bit.ly/31zREVZ ] https://t.co/M5XKxAVGSySoon after the bout, Chandler cut a promo with a pro-wrestling style post-fight interview to put the entire lightweight division on notice. He called out the likes of Conor McGregor, Dustin Poirier and Khabib Nurmagomedov in emphatic fashion.Bleacher Report@BleacherReportMichael Chandler calls out McGregor, Poirier and Khabib after his UFC debut 👀#UFC257(via @ufc)10:44 AM · Jan 24, 202177691109Michael Chandler calls out McGregor, Poirier and Khabib after his UFC debut 👀#UFC257(via @ufc)https://t.co/H1xNLNGmCDThe rest of the fights on the card delivered as well.Women's strawweight contender Marina Rodriguez knocked out Amanda Ribas in the opening bout of the main card. Middleweights Andrew Sanchez and Makhmud Muradov duked it out for two and a half rounds before the latter secured a TKO victory. Joanne Wood edged closer to title contention with a unanimous decision win over former title challenger Jessica Eye.The night, however, belonged to Dustin Poirier. 'The Diamond' not only leveled his series with Conor McGregor at 1-1, but also set up a lucrative opportunity for himself. The promotion looked to immediately book a trilogy bout, which ended up happening at UFC 264.UFC@ufcFrom Day One... #UFC25710:35 PM · Jan 25, 2021177861161From Day One... #UFC257 https://t.co/0b4536cCnu