“He’s always looking for new ways to express the character’s personality,” Mr. Sollima said. “You look at footage after a shoot, and somehow he’s invented this completely different person.”

Mr. Brolin argued that while many actors adopt affectations to personify words on a page, few are as consistently convincing as Mr. Del Toro. “If you try to steal scenes, or stand out, you can lose all respect from everyone,” said Mr. Brolin, who was a contemporary of Mr. Del Toro’s in Stella Adler’s acting classes in the 1980s. “But with Benny it’s the opposite — he’s getting further and deeper into a character that he’s created, and all you want to do as a viewer is invest more and more.”

Mr. Del Toro, who lives in Los Angeles and has a 6-year-old daughter with the socialite Kimberly Stewart, infuses his character work with shards of personal history. DJ, the mercenary hacker he played in “The Last Jedi,” had a distinctive stutter that Mr. Del Toro said was based on that of his father (fan theories about its greater symbolism not withstanding). “We used to imitate him behind his back,” Mr. Del Toro said, meaning him and his brother, Gustavo, now a doctor in Brooklyn.

His father, who still lives in Puerto Rico, was an indirect source for the execution scene in “Day of the Soldado,” too. Mr. Del Toro got the idea for the rapid-fire method years ago, after seeing someone use it at a shooting range.

“I grew up with guns,” he said, recalling shooting bottle targets with the elder Mr. Del Toro on his family’s farm in Puerto Rico. “My father was in the military and my grandfather was a cop — I had a respect for guns, but also an understanding of how dangerous they can be.”