Nicaragua's Felix Alvarado stopped South Africa's DeeJay Kriel after 99 seconds of the 10th round on Saturday to retain his International Boxing Federation light flyweight title.
Making his US debut in Dallas, Texas, Alvarado improved to 36-2 with his 31st stoppage inside the distance.
Alvarado stretched his win streak to 18 fights since losing to Argentina's Juan Carlos Reveco by decision for a flyweight title in June 2014.
Kriel, a former IBF strawweight world champion, fell to 16-2 with one drawn. The 25-year-old from Johannesburg was knocked to the canvas in the second and fourth rounds.
"I knew this would be a tough fight," Alvarado said. "I dropped him with a hook, and I didn't even expect for a punch like that to land. But rather than keep looking for that punch, I kept pushing him to the ropes to wear him down."
It marked the second time Alvarado, whose twin brother Rene fights at super featherweight, has defended the IBF crown he took from Filipino Randy Petalcorin in 2018.
Alvarado, 31, defended for the first time in May 2019 by taking a 12-round decision from Japan's Reiya Konishi in Kobe in May 2019. Alvarado had not fought since then due to the COVID-19 pandemic.
Next on Alvarado's wish list would be a rival world champion, whose ranks include a pair of Japanese unbeatens, WBA super champion Hiroto Kyoguchi and WBC champion Kenshiro Teraji.
"I want any of the other world champions so I can show who is the best in the division," Alvarado said.