Dario is the youngest of Franz Sanchez's three main henchmen and arguably his favorite. A ruthless and psychotic killer, Dario was kicked out of the Nicaraguan Contras for his brutality and found his way into Sanchez's drug cartel as one of his chief enforcers.
Dario was present alongside Sanchez when the latter caught his mistress, Lupe, sleeping with another man in Florida. Sanchez ordered Dario to give Lupe the man's heart and Dario complied by cutting out the man's heart with his switchblade knife. Dario later escaped into hiding when Sanchez was arrested by the Drug Enforcement Administration.
Dario later resurfaces after Sanchez is liberated from U.S. custody by Ed Killifer and Milton Krest. Surprising them on their wedding night, the drug lord has Dario, Braun and Perez kidnap Felix Leiter and murder his wife Della. He is also culpable in the subsequent maiming of Felix by a shark.
- Leiter: "Where's my wife?"
- Dario: "Don't worry. We gave her a nice honeymoooon."
- ―Licence to Kill.[src]
Later on, Dario tries to assassinate one of Leiter's contacts, CIA informant Pam Bouvier, under the guise of hiring her for a job due to her piloting skills. However, the intervention of James Bond disrupts Dario's plans, leading to a bar-room brawl. As Bouvier and Bond flee on a boat moored outside, Dario shoots her in the back and grins to himself sadistically, unaware that she was wearing a kevlar vest underneath her blouse.
Dario makes his final appearance by attending a tour of Sanchez's cocaine processing plant with Bond and a group of Asian investors. Attending the meeting, he notices the undercover spy and covertly holds him at gunpoint during the laboratory demonstrations, pressing a Walther P5 into his spine. His suspicions about Bond's presence are confirmed when Bond sets the lab on fire.
On Sanchez's orders, Dario binds Bond's ankles and wrists with rope and places him on a conveyor belt that drops cocaine bricks into a grinding machine to be mixed with gasoline. After Sanchez leaves, Bond manages to grab hold of the edge, prompting Dario to cut his ropes in order to shove him in. Before he can do so, he is distracted by the sight of Pam Bouvier (whom he believes to be dead) saying
"Ha! You're dead!", who shoots him in the shoulder replying back "You took the words right out of my mouth.", knocking him off his feet. Her gun jams and as he attempts to get back up laughing, Bond grabs him by his feet and pulls him into the grinder. Holding onto Bond's legs, Dario is grabbed by the grinder, which first crushes his legs. This causes Dario to scream in pain, and his death comes immediately afterwards as the rest of his body is ground by the grinder.