Alfonso finished third in the middleweight division at the Cuban Championships in 2017 and third in 2018 and second in 2019 at the Azerbaijani Light Heavyweight Championships.[1][2][3]
Alfonso won the gold medal at the 2019 European Games, defeating Stepan Hrekul, Mikhail Dauhaliavets, Ziad El Mohor, Simone Fiori and Benjamin Whittaker.[4][5] With this success, he qualified for the 2019 World Championships in Yekaterinburg, where he reached the quarterfinals with victories against Gazimagomed Jalidov and Umar Jambekov, before he narrowly lost to Dilshodbek Ruzmetov in the quarterfinals.[6]
At the European Olympic qualification in March 2020 in London, which was interrupted due to the COVID-19 pandemic and continued in June 2021 in Paris, Alfonso won the tournament with victories against Stepan Hrekul and Imam Khataev, as well as advancing without a fight due to the non-appearance of opponents Gazimagomed Jalidov and Benjamin Whittaker, thus qualifying him for the Summer Olympics in Tokyo.[7][8] Competing in the men's light heavyweight event, he defeated Dilshodbek Ruzmetov in the round of 16 and Bayram Malkan in the quarterfinals, before being eliminated in the semifinals by Arlen López, winning a bronze medal.[9]
At the 2021 World Championships in Belgrade, Alfonso won the gold medal in the newly created cruiserweight division. He defeated Tawfiqullah Sulaimani of the Fair Chance Team, Andrei Arădoaie from Romania, Sharabutdin Ataev from Russia, Herich Ruiz from Cuba and Keno Machado from Brazil.[10] He won another World Championship medal in 2023 in Tashkent, after losing to Ataev in the final fight and thus winning silver.[11] At the 2024 European in Belgrade, he won a bronze medal.[12]
At the 2nd Olympic Qualification Tournament in June 2024 in Bangkok, Alfonso defeated Jonathan Tetteh from Ghana, Marko Ćalić from Croatia, Sanjeet Sanjeet from India and Erkin Adylbek Uulu from Kyrgyzstan, thus qualifying for the 2024 Summer Olympics.[13]
