Question: What boxer defeated Gilbert Choombe in the 2012 Olympics along with Manny Pacquiao in a unanimous decision?

Context paragraphs:
Oscar De La Hoya vs. Manny Pacquiao: Oscar De La Hoya vs. Manny Pacquiao, also billed as The Dream Match, was a professional boxing welterweight superfight.  The bout took place on December 6, 2008 at the MGM Grand Garden Arena, Las Vegas, Nevada, United States.  Pacquiao defeated De La Hoya via technical knockout when De La Hoya decided not to continue with the fight before the start of the ninth round.  The card was a co-production of Bob Arum's Top Rank Boxing and De La Hoya's Golden Boy Promotions and was aired live on pay-per-view (PPV) on HBO PPV.  The fight is notable for propelling Manny Pacquiao to full-blown superstar status in much of the western world (mostly in The United States), as Oscar De La Hoya symbolically "passed the torch", so to speak, to Pacquiao.

Jeff Horn: Jeffrey Horn Jr. (born 4 February 1988) is an Australian professional boxer.  He has held the WBO welterweight title since July 2017, after defeating Manny Pacquiao in a unanimous decision.  As an amateur, Horn represented Australia at the 2012 Olympics, reaching the quarter-finals of the light-welterweight bracket.

Manny Pacquiao vs. Brandon Ríos: Manny Pacquiao vs. Brandon Ríos (billed as Fight as One or Clash in Cotai) is a boxing welterweight championship fight for the vacant WBO International Welterweight championship.  The bout was held on 24 November 2013 at the Venetian Macau resort & hotel in Macau.  Pacquiao won via unanimous decision and took the vacant WBO International Welterweight title.  Pacquiao said that the fight would be dedicated to the victims of the recent typhoon hit in the Philippines.  The fight drew 475,000 ppv buys.

Gilbert Choombe: Gilbert Choombe (born 7 March 1992 in Choma, Zambia) is a Zambian boxer.  He competed in the Men's light welterweight event at the 2012 Summer Olympics but lost to Jeff Horn in the first round.

Manny Pacquiao vs. Timothy Bradley II: Manny Pacquiao vs. Timothy Bradley II (billed as "Vindication") is a boxing welterweight championship fight for the WBO Welterweight Championship.  The bout was held on April 12, 2014, at the MGM Grand Garden Arena in Paradise, Nevada.  Pacquiao won by unanimous decision and took the WBO Welterweight title, ending Bradley's undefeated streak.

Manny Pacquiao vs. Jessie Vargas: Manny Pacquiao vs. Jessie Vargas, billed as The Legend/The Champ was a boxing match for the WBO welterweight championship.  The event took place on November 5, 2016 at the Thomas & Mack Center in Las Vegas, Nevada.  Pacquiao won the fight by unanimous decision and took the WBO welterweight title.

Kenny Bayless: Kenny Bayless (born 1950) is an American boxing referee from Nevada.  He is best known for having refereed many of the sport's superfights, including Manny Pacquiao vs. Ricky Hatton, Oscar De La Hoya vs. Floyd Mayweather Jr., Ricky Hatton vs. Paulie Malignaggi, Miguel Cotto vs. Antonio Margarito, Manny Pacquiao vs. Miguel Cotto, as well as Floyd Mayweather Jr. vs. Manny Pacquiao.  Bayless's catchphrase, when giving his instructions to the fighters before the opening bell, is "What I say you must obey."

Manny Pacquiao vs. Óscar Larios: Pacquiao vs. Larios, also billed as Mano-A-Mano and Thrilla in Manila 2, was a professional boxing super featherweight fight held on July 2, 2006 at the Araneta Coliseum, Quezon City, in the Philippines and was a production of ABS-CBN Sports and promoted by Manny Pacquiao Promotions and Golden Boy Promotions.  The judges were Humbert Furgoni from France, Daniel van de Wiele from Belgium, and Noppharat Srichharoen from Thailand with referee Bruce McTavish and ring announcer Michael Buffer.  It was aired live in free-to-air television network ABS-CBN, worldwide through The Filipino Channel, and through pay per view on In Demand, HBO, DirecTV, and SkyCable.  Pacquiao won the fight via unanimous decision, knocking down Larios two times.  The three judges scored the fight 117–110, 118–108 and 120–106 all for Pacquiao.

Manny Pacquiao vs. Shane Mosley: Manny Pacquiao vs. Shane Mosley, billed as The Undaunted, was a welterweight fight for the WBO Welterweight championship.  The bout was held on May 7, 2011, at MGM Grand, in Las Vegas.  Pacquiao defeated Mosley by unanimous decision and retained his WBO Welterweight Championship.  The fight was Manny Pacquiao's first PPV fight in Showtime boxing due to HBO not choosing to air the fight.

Floyd Mayweather Jr. vs. Manny Pacquiao: Floyd Mayweather Jr. vs. Manny Pacquiao, billed as "The Fight of the Century", or the "Battle for Greatness", was a professional boxing match between undefeated five-division world champion Floyd Mayweather Jr. and eight-division world champion Manny Pacquiao.  It took place on May 2, 2015, at the MGM Grand Garden Arena in Las Vegas, Nevada.  Mayweather Jr. won the contest by unanimous decision, with two judges scoring it 116–112 and the other 118–110.  Although the fight was considered to be one of the most anticipated sporting events in history, it was largely considered a letdown by critics and audiences alike upon its broadcast.

Supporting paragraphs: Gilbert Choombe Jeff Horn
Answer: Jeff Horn