Lopez the Heavy (Lopez La Pesado[1] in Spanish) is a main character in Red vs. Blue and is voiced by series creator Burnie Burns. He is a robot built by Sarge with a damaged speech unit that only allows him to speak in Spanish. He served as a supporting antagonist during Season 3 and 4, acting as O'Malley's assistant before returning to the Red Team by the end of Season 5. He was absent during all of Season 8 and had a cameo in 10 before coming back fully in Season 11. 

Initially, Lopez showed great loyalty to the Red Team, until he was possessed by Church. When Lopez tried to escape back to the Reds they attacked him, believing him to be a Blue, leaving Lopez betrayed. With nowhere else to go, Lopez was eventually kidnapped by O'Malley and worked for him for a lengthy period of time. Throughout this period, Lopez's loyalty to the Reds diminished as he grew a more pessimistic view on things.

Lopez's personality has changed since his return to Red Team. He's no longer happy to take orders nor does he commend the Reds as a better team, but instead questions the instructions given to him. He now has taken up the habit of making sarcastic remarks about most of the things people say to him, since nobody understands what he's saying and therefore don't figure out that he's insulting them. Nonetheless, he still follows Sarge's orders and assists the Reds and Blues, even having to save them at times.

However, due to the multiple traumas and disrespect he has received throughout the series, Lopez has developed a grim, apathetic view on life. By Season 5, he had seemingly given up the will to exist, and by Season 11, he had openly resigned himself to the misery the Reds and Blues cause him. In a rare display of fear, however, Lopez appeared extremely alarmed when he discovered Locus was in fact able to understand his insults (a first, since nobody up until then could genuinely understand him), begging the mercenary to not kill him.