Seol Kyung-gu is an actor who possesses a “strange kind of charisma,” whose mere presence on camera evokes a sense of pathos, according to director Byun Sung-hyun of upcoming action flick “The Merciless (Bul Han Dang).”

Having tackled a diverse array of roles and now in the 24th year of his career, Seol is a formidable figure in Korean cinema. But the actor will be the first to admit that his filmography by no means reflects a pristine track.

There were periods when he fell into complacency, following the motions but not putting his heart into his craft, Seol said at an interview at a cafe in Samcheong-dong, Seoul, Wednesday.

“After finishing the filming of ‘Lucid Dream,’ I felt a sudden sense of embarrassment,” he said, referring to the sci-fi drama he starred in last year. “My face went red. Thinking back on my work (for the film). I realized that if I continued this way, I would probably get kicked out of the acting scene.”

The experience was a jolt, he said. 

Seol returns in full form in “The Merciless,” which will screen at Cannes Film Festival’s midnight screenings category next week. His character Jae-ho is a complicated figure -- maniacal, brutal, damaged and cunning -- that Seol portrays with both the gusto of his earlier years and a newfound gravitas.

As in Seol’s past roles, a sense of wretchedness underlies Jae-ho, the ruthless drug kingpin who grows dangerously fond of a young delinquent, played by Im Si-wan, with questionable intentions seeking to join his operation. But this time round, Seol says, he is more “polished” than ever before.

When he first met with Byun to discuss the film, the director had remarked that Seol seemed “too crumpled up, wrinkled.”

“(The director) said he wanted to flatten me out, make me stand taller,” said Seol. “I think he meant many things by that.

“So for the role, I was put in an expensive suit. I wore an expensive watch, my hair was combed back. It was incredibly uncomfortable at the beginning … but I discovered that your body movements change according to your clothes.”

Seol has rarely taken on clean-cut roles. He rose to acclaim around 2000 after portraying the demise of the idealistic youth Yong-ho in the 1999 film “Peppermint Candy,” and cemented his reputation as both an uncanny talent and a box office hit-maker in 2002 with roles like the roguish detective in “Public Enemy” and the mentally challenged delinquent in “Oasis.” He went through a massive physical and methodical transformation in “Rikidozan: A Hero Extraordinary” when playing the professional Japanese wrestler, gaining some 30 kilograms and learning Japanese.

The actor has stayed active in recent years, starring in hits like the 2009 disaster film “Haeundae,” and box office misses like the 2015 war film “The Long Way Home,” and many more. 

The character Jae-ho, though he may appear to be on the verge of psychopathy with his high-pitched laugh and killing spree, is to Seol a “calculating” character, he said.

“But he can’t help himself when it comes to Hyun-soo,” said Seol of Im’s character.

The film has been described as a bromance-slash-romance between the two characters. “It’s love, I think,” said Seol, though not necessarily a romantic love. “I viewed the film as a coming-of-age of Hyun-soo. It deals with his evolution. Jae-ho acts as a sort of mentor to him. (Hyun-soo) becomes someone who he would go to all lengths to protect even though he knows he’s being tricked.”

This year marks Seol’s fourth presence at Cannes, after “Peppermint Candy” (2000), “Oasis” (2002) and “A Brand New Life” (2009).

“The Merciless” will open in local theaters on May 18.

By Rumy Doo (doo@heraldcorp.com)