While there have been many to choose from, the knockout of UFC Featherweight Champion Jose Aldo by Conor Mcgregor at UFC 194 is the one major knockout that sticks out in 2015. Ironically, the event happened near the end of 2015 on December 12 at the MGM Grand Garden Arena in Las Vegas, NV. The fight only lasted 13 seconds, as McGregor caught Aldo early with a left hook and followed with a few hammer fists that quickly ended the reign of the 145 pound division emperor. It was billed as the most anticipated fight of the year, and it just also happened to be one of the shortest.
Jose Aldo (age 29) previously had a record of 25-1, and hadn’t lost fight in ten years. Aldo won the World Extreme Fighting Featherweight Title in 2009 against Cub Swanson, which he defended twice before organization was merged into the Ultimate Fighting Champion. As the UFC Champion, he defended the belt 7 times and became the highest pound for pound ranked in the organization. However, he came into the fight as the underdog against the Irish knockout superstar Conor McGregor (age 27). McGregor and Aldo were supposed to face either back in July, but Aldo pulled out the fight due to a rib injury. McGregor instead fought former Aldo rival Chad Mendes whom he knocked out in the second round for the Interim Title.
McGregor has record of 19-2 and is currently 7-0 in the UFC after defeating Aldo to become the new Featherweight ruler. McGregor had been Featherweight Champion of the London based organization Cage Warriors who won by submitting Dave Hill with a rear-naked choke. The win was unusual for McGregor who normally wins with knockouts. Though he does use kicks for knockouts, McGregor primarily relies on his punching power and has the highest KO percentage (89%) of any MMA fighter in a major promotional organization. McGregor’s quick knockout of Aldo is even more impressive since the former was known for having durable chin, especially against the hard-hitting Mendes . McGregor is now expected to fight for the Lightweight Title against Rafeal Dos Anjos at UFC 197 in March 2016.
(sources: http://www.sherdog.com/fighter/Conor-McGregor-29688, http://www.sherdog.com/fighter/Jose-Aldo-11506,http://www.sherdog.com/news/articles/1/Sherdogcoms-2015-Knockout-of-the-Year-97775)