The nickname says it all. “Marreta” means sledgehammer in Portuguese.

Thiago Santos established a reputation as a reliable competitor with a penchant for sudden violence upon arriving in the Ultimate Fighting Championship six-plus years ago. He started his ascent in the middleweight division, where he compiled a 10-5 record across his first 15 appearances inside the Octagon—a run that included victories over “The Ultimate Fighter Nations” winner Elias Theodorou, onetime Strikeforce champion Nate Marquardt and former Cage Warriors Fighting Championship titleholder Jack Hermansson. However, Santos shed the weight cut, moved to 205 pounds and morphed into something the UFC desperately needed: a legitimate threat to the man who occupied the light heavyweight throne.

In a career that has resulted in a number of defining moments, here are five that stand out:

1. Inauspicious Start

Cezar Ferreira spoiled Santos’ promotional debut, as he submitted “The Ultimate Fighter Brazil” Season 2 quarterfinalist with a guillotine choke in the first round of their UFC 163 middleweight showcase on Aug. 3, 2013 at the HSBC Arena in Rio de Janeiro. A replacement for the injured Clint Hester, “Marreta” surrendered 47 seconds into Round 1. Ferreira wasted no time getting down to business. He staggered Santos with a clubbing left hook during their opening exchange and progressed toward a finish. Santos dove for a desperate takedown, only to find himself trapped in an arm-in guillotine choke. Soon after, he asked out of the match, resulting in the first submission defeat of his career.

2. Mr. Freeze

Santos knocked out Steve Bosse with a violent left head kick in the first round of their UFC Fight Night 70 middleweight feature on June 27, 2015 at the Seminole Hard Rock Hotel and Casino in Holloway, Florida. The Brazilian drew the curtain 29 seconds into Round 1, as Bosse paid a severe price for his lack of defensive wherewithal. Less than half a minute into the match, Santos fired a kick to the body that coaxed the Canadian’s hands out of position. The head kick came next, a sickening thud of shin smacking skull echoing through the arena. Bosse dropped to the canvas stiff and unconscious, the former hockey player’s run of eight straight victories having met a most unceremonious end.

3. Lion Tamer

Some victories age better than others. Case in point: Santos’ technical knockout of Anthony Smith in the second round of their main card pairing at UFC Fight Night 125 on Feb. 3, 2018 in Belem, Brazil. “Lionheart” bit the dust 63 seconds into Round 2, the victim of a crushing liver kick and follow-up punches. Both men found themselves in peril in the first round, where Smith ate a pair of head kicks before somehow falling into full mount. Santos reversed into top position, tore into the former Cage Fury Fighting Championships titleholder with body-head ground-and-pound and returned to his feet. The two middleweights connected with dueling right hands in the final minute, as Santos suffered a significant gash on his left eyebrow and Smith hit the deck. Undeterred by the cut, Santos sent a kick sweeping across the American’s midsection early in the middle stanza. Smith doubled over and retreated in noticeable pain, his adversary in hot pursuit. Santos uncorked punches with the Factory X representative clinging to his leg in a seated position, and after a sustained volley of unanswered blows, referee Marc Goddard had seen enough. Smith later moved to the light heavyweight division, where he enjoyed a resurgence, emerged as an unlikely title contender at 205 pounds and provided a roadmap to success for his Brazilian counterpart.

4. Front of the Line

Maybe fights with Santos should come with warning labels attached. “Marreta” stepped up his climb on the light heavyweight ladder, as he took care of former KSW champion Jan Blachowicz with punches in the third round of their UFC Fight Night 145 headliner on Feb. 23, 2019 at the O2 Arena in Prague. Santos made the Pole his latest victim 39 seconds into Round 3, recording his third consecutive finish. Blachowicz performed well for two-plus rounds but decided to press his luck in the third and lived to regret it. The seasoned veteran overextended on an uppercut and left himself vulnerable to a Santos counter. The opportunistic Brazilian floored Blachowicz with a left hook, trailed him to the canvas and assaulted him with rapid-fire hammerfists to prompt the stoppage. With that, the UFC had a new No. 1 contender at 205 pounds.

5. Tough Pill

Jon Jones looked mortal for 25 minutes. The divisive Jackson-Wink MMA superstar successfully defended his light heavyweight crown in the UFC 239 main event, where he escaped with a split decision over Santos on July 6, 2019 at T-Mobile Arena in Las Vegas. All three judges scored it 48-47: Michael Bell and Derek Cleary for Jones, Junichiro Kamijo for Santos. Jones seemed content to play with fire on the feet, and though he was the advancing party for much of the match, he was less active in terms of output. Despite suffering a serious knee injury—he tore three ligaments and his meniscus—in the first round, Santos nearly doubled the champion in attempted strikes (166-90) but landed 16 fewer of them. Statistically, Jones did his best work in the third and fifth rounds, as he controlled range, picked his spots and connected at an efficient 75-percent clip.