Tuco Salamanca Was a well known member of the Mexican drug cartel and an individual who had a violent unpredictable personality. Tuco was treated like a son by his Uncle Hector who groomed his nephew to eventually take his place in the organization. Tuco also had a good Relationship with his grandmother Aubelita.
When Cal and Lars Lindholm tried to con Aubelita (ignoring Jimmy Mcgill's instructions to target the Kettlemans), Tuco forced Jimmy inside at gunpoint and was about to let him go when one of the twins said that the whole thing was planned and claimed Jimmy was the mastermind. Tuco then dragged Jimmy and the Lindholms out into the desert. Tuco was convinced by his underling Nacho Varga to let Jimmy live and Jimmy talked him into sparing the twins' lives. Tuco still felt a message needed to be sent and broke both boys' legs.
Nacho became increasingly concerned with Tuco's unstable and violent behaviour, so he contacted Mike Ehrmantraut to take his boss out. However in order to avoid the wrath of the cartel Mike found an alternative solution, by deliberately provoking Tuco into attacking him and getting him sent to prison.
Hector paid Mike to lie and get Tuco a shorter sentence, but Tuco's brutal stabbing of another prisoner caused him to be placed into solitary and added a while on to his sentence.
After getting out of prison, Tuco became one of New Mexico's biggest meth distributors. Walter White instructed Jesse Pinkman to meet with Tuco. After realising that Tuco had no intention of paying, when Jesse tried to leave with the meth, Tuco brutally beat him and put him in a hospital. Following this Walt used explosives against Tuco and coerced him into an uneasy partnership.
When one of Tuco's henchman No-Doze spoke out of turn Tuco Savagely killed him. Growing worried about betrayal, Tuco kidnapped Walt and Jesse, taking them to Hector's house in the desert. Walt and Jesse's attempt to poison Tuco was thwarted by Hector. After learning about the plan to kill him, Tuco began to beat Jesse who knocked him down. After getting back up Tuco approached Jesse's car and was met by DEA agent Hank Schrader. Tuco attempted to shoot Hank who promptly Killed him in self-defense.