Marco and Leonel Salamanca

"We've waited long enough. We won't wait any longer."

- Marco to Gustavo Fring after being denied the assassination of Walter White

"No. Too easy."

- Marco's last words

Leonel and Marco Salamanca (commonly known as The Cousins) were twin brothers and hitmen for the Juárez Cartel, a Mexican drug cartel and villains in Breaking Bad. Despite an austere, mechanical physicality and virtually non-verbal interaction, they were a fearsome presence who killed without hesitation or emotion. They served as the main antagonists of the first half of Season 3.

They were portrayed by Luis and Daniel Moncada, who are brothers (though not twins) in real life as well.

History
They serve as the main antagonists of the first half of the third season of Breaking Bad. In their first appearence, it is shown that they plan on killing the renowned meth cook Heisenberg (aka Walter White), as revenge for betraying and causing the death of their cousin, Tuco Salamanca. Throughout the next few episodes, they are shown preparing to take down Walter by attempting to discover his location, so that they can carry out their revenge. At one point, they finally discover where Walter lives and prepare to kill him before being asked to stop on their boss's orders. Soon after, they arrange a meeting with Walter's boss, Gustavo Fring, in order to receive his permission to kill his cook. Unfortunately for them, Walter is too valuable to Fring, but he gives them permission to kill Hank Schrader (Tuco's direct killer) as compensation. They then track down Hank to a parking lot and proceed to carry out the hit, but due to a forewarning from Fring, Hank gains the surprise upper hand and manages to kill Marco and severely injure Leonel. After the attack, Leonel is finished off by Gus's goon, Mike Ehrmantraut, and their boss, Juan Bolsa, is killed thanks to manipulation on the part of Gus.

After their deaths, it is revealed late in the fourth season that Gus betrayed the two in order to exact revenge on their uncle, Hector Salamanca, for the death of his friend, Max, whom Hector had killed years ago. Gus then proceeds to torture Hector about the deaths of Tuco, Marco, Leonel, and Joaquin (Hector's grandson who was killed by Jesse Pinkman) in order to complete his revenge against him and the cartel.

Personality
Leonel and Marco Salamamca were raised on the importance of the family being all by their uncle, Hector and anyone who crossed them deserved to die. This life lesson which was taught to them as children acted as fuel for their revenge against Walter White, then later Hank Schrader who betrayed and killed their cousin, Tuco Salamamca. As hitman for the cartel, The Cousins are hardly fazed by any of the atrocious acts they are ordered to do, they remain calm, stoic, emotionless, apathetic and ruthless even in dangerous situations. They have a mechanical, almost synchronised connection and rarely speak, only when it is needed.