Honourable Mentions:

Bas Rutten – an MMA pioneer from the Netherlands who fought initially in Japan under the Pancrase banner, ‘El Guapo’ made his way into the UFC in 1999. Two fights and a controversial decision later, and he was the UFC Heavyweight champion. Unfortunately, injuries prevented him from ever defending the title and forced him into a premature retirement, meaning he couldn’t really cement himself as a UFC legend. He went on to become one of MMA’s most well-known commentators and has been inducted into the UFC’s Hall of Fame.
Mirko Cro Cop – The Croatian kickboxer is widely recognised as one of the greatest Heavyweight MMA fighters of all time, and his list of victims – Mark Coleman, Kevin Randleman, Igor Vovchanchyn, Wanderlei Silva, Josh Barnett – reads like a who’s who list. But the majority of his success came in Japan inside the PRIDE ring, and in the UFC his record was a poor 5-6, which keeps him off this list.
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Germaine de Randamie – I felt I had to include her given she did win a UFC title, although her reign was both short and controversial as she gave the title up rather than face Cristiane Justino. Recognised as a world-class kickboxer, de Randamie built a record of 5-2 at 135lbs across StrikeForce and the UFC before beating Holly Holm for the inaugural Women’s Featherweight title this February. But due to her spotty record and her lack of title defences, she can’t make the top five.
Andrei Arlovski – With his flowing hair, thick beard and fanged mouthpiece, Arlovski was one of the most recognisable and fearsome fighters on the UFC roster as the TUF boom exploded in 2005. He captured the Heavyweight title with a win over Tim Sylvia and then defended it twice, but lost it back to Sylvia a year later. Arlovski left the UFC to become one of the sport’s highest-paid fighters in 2008, and a string of losses outside the promotion seemed to signal an end to his career. But he returned to the UFC in 2014 and resurrected himself with four straight wins. He’s still competing and remains ranked in the top 15 today.