McWilliams Arroyo

Immediately afterwards, both pugilists competed in a third contest as part of the first Juan Evangelista Venegas Olympic Cup. This event was organized by the Olympic Committee of Puerto Rico (COPUR), serving as the final qualifier to determine who would enter Puerto Rico’s national team in preparation for the 2009 World Amateur Boxing Championships. The first two rounds concluded with a close score of 5:4, which favored Arroyo. In the third round, González connected a right hook and scored a knockdown. Arroyo stood up while still affected by the punch and was forced to receive a protective count following another offensive barrage. With the score favoring him by two points 7:5, González scored three more times, while Arroyo was only able to do so once, securing a final score of 10:6. Subsequently, the Federación de Boxeo Aficionado de Puerto Rico (lit. "Amateur Boxing Federation of Puerto Rico") selected Arroyo to participate in the World Amateur Boxing Championships over González. Both of the brothers participated in this international event. Arroyo debuted in the tournament's third date, defeating Yoon Kyoung Min of Korea by RSCH in the second round. To close the preliminaries, he won his contest against Norbert Kalucza of Hungary by RSC in the third round. In the quarterfinals, Arroyo defeated Yampier Hernández by points, 6:2. He advanced to the finals by winning his fight against Ronny Beblik of Germany (9:7). Arroyo won the tournament's flyweight gold medal, defeating Tugstsogt Nyambayar of Mongolia with a score of 18:2, the widest margin in all of the finals.

Arroyo began competing in the 70 pounds division, while his brother did so in the 75 pounds. He participated in the first Pan-American Cadet Championships, representing Puerto Rico in the event held in Mexico. In this competition, Arroyo won his first medal in an international tournament, earning the silver medal. Subsequently, he performed in the International Junior Olympics held in Michigan, where he won his division's gold medal. Arroyo entered the V José "Cheo" Aponte Tournament held from June 1–7, 2003. He advanced to the finals, losing a close decision to Joseph Serrano (13:14) to win the silver medal. Arroyo also represented Puerto Rico in the Copa La Romana, organized in La Romana Province, Dominican Republic, earning the event's silver medal. In 2003, he was named Puerto Rico's Youth Boxer of the Year. Arroyo entered the 2005 Torneo Batalla Carabobo where he won the event's silver medal. The VII José "Cheo" Aponte Tournament was held between June 2–7, 2005. In the semifinals, Arroyo defeated José Meza of Ecuador, 17:13. He won the gold medal, defeating Steven Ortíz by points (25:16) in the finals. Arroyo competed in the 2005 Pan American Championships, earning his division's silver medal.

Arroyo recovered with a six round unanimous decision win over Jiovany Fuentes. To open 2011, he scored a first round knockout over César Grajeda. Arroyo followed this with five round win over Erickson Martell. He closed the year with seven and two round technical knockouts against Rigoberto Casillas and Lorenzo Trejo. Arroyo won his next contest against Gilberto Mendoza, when the latter retired after suffering a shoulder injury. On March 10, 2012, he defeated Luis Maldonado to win the World Boxing Organization's Latino title. After repeating his previous performance in a rematch with Casillas, Arroyo defended the championship by knocking Ronald Ramos out in five rounds. On February 2, 2013, he won the World Boxing Council's Latino title with a four round win over Miguel Tamayo. However, Arroyo suffered an injury in his right hand and afterwards entered a prolonged inactivity. His return took place in an International Boxing Federation title eliminator on June 19, 2014, where he defeated Froilan Saludar by knockout in two rounds.

His next competition was the Torneo Nacional de Boxeo Aficionado Isaac Barrientos, Puerto Rico's national championship tournament. In the finals, he was matched against AIBA Youth World Champion, Jonathan González. Early in the contest, González was able to use his speed and counterattack to establish control of the fight's tempo, winning the first round 3:0. This pattern continued in the next stanza, where he was able to score six more points, including three in only eighteen seconds, before his opponent scored his first point. Arroyo attempted to pressure the fight on the third, reducing the difference to 9:4, before González had one final advance, securing the final score of 11:5. Arroyo returned to action at the XII José "Cheo" Aponte Tournament, which began on May 19, 2009. Prior to the competition, the local media emphasized the rematch between him and Arroyo, labeling them as "nemesis". After advancing to the finals, he was matched against González, who won the second bracket. On this fight, Arroyo was able to win by points, gathering rounds of 6:3, 12:6 and 17:9. The fight was described as "frenetic" and saw a change in strategy by González, who attempted to pressure the offensive.

On December 8, 2009, the Arroyo brothers issued a press release through their mother, Milagros Acevedo, informing that they were no longer interested in continuing their amateur careers. In the letter, they report differences with the criteria used to provide economical support to high-performance athletes, as well as schedule conflicts with their original plans to pursue a professional career after the 2010 Central American and Caribbean Games. These concerns were restated in a subsequent press conference, where they noted that supporting their respective families was the main reason to pursue a professional career. On January 12, 2010, PR Best Boxing announced the official signing of both brothers. Arroyo's debut was scheduled for February 27, 2010, taking part of a card titled "Haciendo Historia", where Wilfredo Vázquez, Jr. fought Marvin Sonsona for the super bantamweight world championship. His opponent, Eliecer Sánchez, also debuted as a professional in this card. The fight concluded after 1:46 of the first round had passed, when Arroyo connected a single punch that left Sánchez unconscious for several minutes, requiring paramedical help and an oxygen mask, this result earned him a victory by knockout. In his second fight, he was matched against the latest Dominican Republic Minimumweight Champion, Francisco Rosario. Arroyo won by technical knockout in the third round, when Rosario surrendered following an exchange of solid combinations. His next opponent was Samuel Gutiérrez, who was forced on the defensive from the opening round, receiving several combinations and suffering a broken nose. In the second, Arroyo continued on the offensive, scoring a knockdown which prompted the referee to stop the fight. In his next fight, he suffered an upset loss to Takashi Okada (1-0-1) who knocked Arroyo down in the second round en route to a unanimous decision victory.

The Arroyo twins, McWilliams and McJoe, qualified to the 2008 Summer Olympics due to their performance at the AIBA World Championships. It was the second time that twins competed in an Olympic boxing tournament, the first pair being Valeriy and Wladimir Sidorenko, who participated together in the 2000 Summer Olympics. On July 2, 2008, Arroyo was selected to carry Puerto Rico's flag in the opening ceremonies of the Olympics. On July 8, 2008, Puerto Rico's Sports and Recreation Department offered up to $48,000 to the five boxers classified to the Olympics, if the boxers choose to continue with the team for a second Olympic cycle. In respect, Arroyo expressed that he would make his decision after comparing the offers provided by the government and professional promoters. The twins, José Pedraza and Jonathan González began their preparations in a massive sports complex located in Salinas, Puerto Rico, named Albergue Olímpico. During the training, Arroyo suffered an injury in one of his legs. Consequently, his right foot underwent surgery and two screws were fasted to his bone, interrupting his training regime. As part of their training the boxing team moved to South Korea, in order to get used to the time changes. Arroyo joined them and officially received the flag of Puerto Rico that was going to be used in the Olympic games on July 9, 2008. After training and participating in a series of exhibition matches, the team traveled from South Korea to Beijing. Despite the surgery, Arroyo decided to compete in the Summer Olympics along his brother. He received a bye in the first round of the preliminaries. Arroyo debuted in the final stage of the preliminaries, defeating Norbert Kalucza of Hungary, 14:6. In the quarterfinals, he lost to Andry Laffita (11:2). Arroyo subsequently continued the rehabilitation process and the following month, his first son was born, receiving his namesake, McWilliams Arroyo Junior.

Both of the twins classified to the 2006 Central American and Caribbean Games. Arroyo debuted in the light flyweight semifinals, defeating Yan Bartelemí of Cuba, 14:11. After advancing to the finals, he earned the tournament's gold medal, winning his contest against Odilion Zaleta of Mexico by points (14:8). His brother won the bronze medal at the 112 lbs division. For this performance, Arroyo won Puerto Rico's Boxer of the Year recognition. The IX José "Cheo" Aponte Tournament was held between May–5, 2007. In the quarter finals, Arroyo defeated Juan Carlos Payano of the Dominican Republic, 20:12. He won his semifinals against Alex Ferramosca of Italy (26:6). In the finals, Arroyo defeated Juan Vega of Ecuador by points, 30:14. Prior to the 2007 Pan American Games, both of the brothers moved up one division in order to avoid being matched against each other in local tournaments. Arroyo, now fighting at the flyweight division, debuted in the tournament's first date, defeating Lucas Navarro of Argentina by AB in the second round. He won his bracket's quarterfinal against William Urina of Colombia, 16:7. In the semifinals, Arroyo defeated Yoandri Salinas by RSCH in the second round. He gained the tournament's gold medal, winning by 12:11 against Juan Carlos Payano. Both of the brothers participated in the 2007 World Amateur Boxing Championships. Aroyo debuted in the tournament’s third date, defeating Luvsantseren Zorigtbaatar of Mongolia by points, 26:10. He won his second preliminary contest against Vitali Volkov of Ukraine (23:14). Arroyo closed his participation in this round by defeating Bato-Munko Vankeev of Belarus, 23:17. In the quarter finals, he lost to Samir Mammadov (33:21). McJoe Arroyo advanced, winning the tournament's bantamweight bronze medal.

McWilliams Arroyo Acevedo (born December 5, 1985) is a Puerto Rican professional boxer who has challenged twice for a world flyweight title, in 2014 and 2016. As an amateur, Arroyo represented Puerto Rico in numerous international events.