Allende is the colonel of the Mexican Army and the provincial governor of the state of Nuevo Paraíso under the Mexican President, General Ignacio Sanchez. He is responsible for suppressing the rebellion in the Nuevo Paraiso territory led by Abraham Reyes, and doesn't care whom he hurts in order to achieve his goals.
Many years ago, Allende was an idealist, but he's become a vicious cynic with a love of torture and sexual abuse. He takes pleasure in all manner of vices, and despite being corrupt and brutal, he is also quite intelligent. Allende lives in a high-class, fortified mansion on the highest ground of Escalera, enabling him to oversee the entire city from the comfort of his front porch. It is known that Javier Escuella works for Allende as a hitman for hire.
By the time John Marston arrives in Mexico on the hunt for his old gang members, Escuella and Bill Williamson are already under his protection. Instead of killing him, Allende decides to manipulate John into aiding him against the rebels led by Abraham Reyes.
Events of Red Dead Redemption
After Marston's venture to Mexico, he decided to partly work with Allende, who promised to deliver Escuella and Williamson to John. Allende took advantage of John's skills to go on numerous missions with Captain Vincente de Santa and Captain Espinoza and his many soldiers to massacre the rebels and capture young women for his "personal pleasure". Eventually, Allende met with John personally, claiming he has captured Escuella and Williamson and that they were being held in a church ready for Marston to do whatever he wanted with them. However, Allende secretly betrayed him having ordered De Santa to kill him after they arrived at the church. Marston's execution was interrupted by Abraham Reyes and his rebels just in time. While Captain De Santa escaped, Reyes, along with Marston and the rebels, took out all of Allende's soldiers along with Captain Espinoza.
Marston subsequently sided with the rebels and Reyes, who promised he would find Escuella and Williamson. While working with the rebels, Marston began helping them by killing more of Allende's soldiers, killing Captain De Santa, and either killing or capturing Escuella. Soon, the rebels made the attack on Allende's villa, killing every one of his soldiers in the process, causing Allende and Williamson to lock themselves within the villa. Once the rebels broke down the door to the villa, Allende and Williamson tried to escape in an armored stagecoach accompanied by three guards. Marston and Reyes chased after them on their horses, killing the Colonel's guards and the driver of the carriage, causing it to stop. Allende, fearing for his life, surrenders from inside the carriage. He forces Williamson out of the carriage and then proceeds to pin him on the ground with his foot. The Colonel tries to bargain with them, saying that Williamson was the one Marston wanted and promises Reyes that he will flee the country.
Allende is then killed by either John Marston or Abraham Reyes, depending on whether the player decides to shoot him, or hesitates and allows Reyes to shoot him instead.
In "It is the way of mankind, a fight between two forces", Allende may be an allusion to The Communist Manifesto, written by Karl Marx and Frederich Engels in 1848. This line parallels the statement at the beginning of the first chapter; "The history of all hitherto existing society is the history of class struggles."
It is possible that Allende was once a communist, or at least interested in communism. He claims to have been a "radical idealist" in the past, communism being a radical, left-wing ideology. Additionally, he was formerly a peasant, which may have given him incentive to become interested in communism.
Given that Javier Escuella is a socialist revolutionary of sorts (history of revolutionary activity, advocating that wealth should be shared more evenly, admiring Dutch and his Robin-Hood-like ideas etc.), it is quite possible that Allende shares these far-left ideals, which would explain why Javier chose to work for him.
A pre-release artwork of Colonel Allende shows him to be originally a little different. In the artwork, he is shown a bit fatter than he is in the game. The artwork also show Allende's uniform originally lacked epaulets.
Allende owns a golden sword and an armor-plated stagecoach with a Gatling Gun on the back of it. Its only appearance is in the mission "An Appointed Time".
Even after Allende has been killed, his portrait will still hang inside his villa, hinting that the Rebels did not decide to occupy it.
According to Reyes and at times random NPCs, Allende ironically used to be a poor peasant. This contrasts with Reyes, who was born wealthy and is now leading the peasants in revolution.
Allende is described as "General Sanchez's dog" on one of the rebels' propaganda-posters.
After leaving Escalera after "An Appointed Time", Allende's corpse can be seen in the middle of the road out of town.