This interview contains spoilers for the Season 5 finale of “Better Call Saul.”

Cheerful, easygoing and sociopathic, Eduardo “Lalo” Salamanca has caused agita for just about everyone in “Better Call Saul” since he showed up in Albuquerque last season. By the end of the Season 5 finale, which aired Monday, he had survived the crew of assassins dispatched to his home in Mexico by his arch nemesis and drug-trade rival, Gus Fring.

The clash ended poorly for the assassins — Lalo killed them all — and very well for Tony Dalton, who has turned Lalo into the sort of irresistible rascal you hate yourself for loving.

The role is a breakthrough for Dalton, 45, a standout in what is easily the most compelling season yet of “Better Call Saul,” a prequel to “Breaking Bad.” Until last year, Dalton was largely invisible to American audiences, aside from brief appearances in “Sense8,” a sci-fi drama on Netflix. Raised in Mexico City and educated at a private school in Massachusetts, he studied acting briefly at the Lee Strasberg Theater & Film Institute in Manhattan, and then headed to Los Angeles. There, he confounded a lot of casting directors.

“I have this thing that’s sort of chased me around,” he said on the phone last week. “‘Well, you don’t look that Mexican, you don’t sound Mexican, but you are Mexican. So, do we give you a Mexican part or do we give you an American part?’ It’s been the bane of my existence as an actor. It finally worked in my favor.”