Dubbed Korea's John Cena, the musical star turned hard-boiled mainstay came up through intense poverty Kim Moo-yul (Prain TPC) There's a particular man Korean directors keep asking Kim Moo-yul to play: rough on the surface, colder underneath, the kind of tough guy who solves problems with his fists and rarely needs to raise his voice. He's been some version of that figure for the better part of 15 years, often the live wire of the work and almost always the face you remember on the way out.So it makes perfect sense that a pulpy revenge fantasy about a government unit that beats the country's worst students back into line would land in his lap. His latest series, "Teach You a Lesson," is currently the biggest thing on Netflix outside the English-speaking world: No. 1 on the platform's non-English chart for weeks running, more than 20 million views and a top spot in dozens of countries. "Teach You a Lesson," starring Kim Moo-yul (Netflix) Kim plays Na Hwa-jin, a former special-forces operative turned school inspector who handles what the system can't, stepping in whenever bullies and unruly kids spiral out of control and restoring order with his fists. He's also picked up some unexpected meme status along the way, thanks to his resemblance to WWE star John Cena. (After fans kept flagging it, Cena posted Kim's photo on Instagram without a caption, to which Kim replied, "Now you can see me.")That viral moment buries an unlikely backstory. Further back in Kim's life sits a stretch he rarely brings up on his own: an adolescence and early adulthood marked by deep hardship.Barely getting byBorn in Seoul in 1982, Kim ran track in middle school before setting his sights on acting early, over his father's objections. With his mother quietly covering for him, he took acting lessons through his teens and enrolled at Anyang Arts High School.That was the easy part. Around the time he started high school, his family's finances came apart in the fallout of the Asian financial crisis; worse, his mother was swindled in an investment scheme, leaving the family heavily in debt. Money got so tight that she had to borrow from neighbors just to put together her son's bus and subway fare, Kim recalled on the talk show "You Quiz on the Block" in 2024.College years brought the lowest stretch. After his father collapsed and never fully recovered, the family moved to a hillside shanty settlement outside Seoul, at one point leaning on neighbors for rice and fuel. Kim had to put his acting studies at Sungkyunkwan University on hold, taking whatever work he could find: delivery runs, janitor shifts, construction sites and street-vending."I've worked more jobs than I can remember," he said on the talk show. "It kept happening, over and over, and as the eldest son, I just kept telling myself I had to get tougher." Kim Moo-yul (right) speaks during a 2024 appearance on tvN's "You Quiz on the Block." (tvN) But Kim never quit acting through any of it. The hourlong walk home from the train station became his ad hoc rehearsal session as he ran lines and worked scenes the whole way."Looking back, I think it was my only way out," he said of those nightly walks.The struggle didn't let up even once he found his footing onstage. Even after he'd started making a name in musicals, the family stayed in debt; his father, diagnosed with cancer in 2008, died in 2010.Most of this story only reached the public in 2012, when a state audit questioned the poverty-based exemption the actor had been granted in 2011, given how much he was earning by then. As allegations of draft dodging brewed, Kim laid out the full account of those hard years, with multiple former friends and neighbors confirming it.Though he was cleared in the end, Kim enlisted voluntarily in 2012 anyway, serving his full term in the South Korean army before his discharge in 2014.Stage to screenKim cut his teeth in Daehangno, Seoul's bustling small-theater district and a launchpad for plenty of names now familiar from the screen. He featured in repertory staples like "Subway Line 1" and "Assassins," and by the close of the 2000s, he'd become a fixture in the local musical scene.He left a strong impression as the cold, calculating lead in the Korean staging of Stephen Dolginoff's murder-pact two-hander "Thrill Me," and won best actor at the 2009 Korea Musical Awards for the rock musical "Spring Awakening." Kim Moo-yul (center) performs in the musical "Spring Awakening" in 2009. (Musical Heaven) Film and television came calling around that time. He broke onto the big screen with a scene-stealing supporting role in the stock-market thriller "The Scam" (2009), playing a slick young trader, a turn that earned him a best-new-actor nomination at the Blue Dragon Awards. The same year, he played the main villain in the sprawling network drama "Wife Returns."Playing it toughKim worked relentlessly through the 2010s, especially on the big screen, with his sharpest roles clustered in crime and action. At the lighter, crowd-pleasing end, he played them with a brash, pulpy swagger: the maverick cop who teams up with a thug (Ma Dong-suk) to corner a serial killer in "The Gangster, the Cop, the Devil" (2019), or the slick, slimy mastermind of a phone-scam ring in "On the Line" (2021). Kim Moo-yul stars in "The Gangster, the Cop, the Devil" (Twinfilm) Streaming put him in front of a far bigger crowd in the 2020s. In the Netflix series "Juvenile Justice" (2022) — the same Hong Jong-chan production that would later reunite him with co-star Lee Sung-min for "Teach You a Lesson" — Kim played a soft-hearted juvenile-court judge, the gentler counterweight to Kim Hye-soo's iron-fisted one. He also signed on for the streamer's apocalyptic horror series "Sweet Home" across its final two seasons, playing a hardened special-forces sergeant in a monster-hunting unit. Kim Moo-yul stars in "Juvenile Justice" (Netflix) 2024 was Kim's banner year. Back opposite Ma Dong-suk, Kim showed up as the arch-villain in "The Roundup: Punishment," the latest entry in the wildly popular franchise. His Baek Chang-ki was the cold-blooded boss of an overseas gambling racket who cut down nearly everyone in his path before a brutal showdown with Ma.The film blew up in an otherwise bleak year for Korean theaters, drawing 11.5 million admissions at home and selling to more than 160 territories abroad. More than any single role, it cemented what the actor is now best known for: a formidable, ice-cool screen presence with the finely chiseled physique to back it up. Kim Moo-yul stars in "The Roundup: Punishment" (PlusM Entertainment) "My confidence never wavered," Kim said of the role in an interview around the film's release. "Whatever role they handed me, I believed I could pull it off. If I got too hung up on measuring my character against the ones before him, I'd have nothing new to show. So I kept what worked about them and let go of whatever felt like a weakness."This isn't to say the tough guy is his only trick; he's shown a subtler, more nuanced side as well. In "Eungyo" (2012, released abroad as "A Muse"), Kim played a writer consumed by envy of his elderly mentor, a rivalry equal parts artistic and sexual. And in the memory-bending thriller "Forgotten" (2017), he took on a brother who goes missing and returns home a different man, a double-edged performance anchoring the work's central mystery.A love story by accident Kim Moo-yul (left) and Yoon Seung-ah in 2025. (Dofwlw on Instagram) Kim is married to fellow actor Yoon Seung-ah ("Playful Kiss," "Moon Embracing the Sun"); the two have a son. For an actor who's built a career on heavy material, the way that romance came to light is disarmingly sweet.The story goes back to 2012, when a tender late-night message Kim meant to send Yoon privately went out as a public tweet instead, a gushing, lovestruck note plainly written for an audience of one. The agencies confirmed the relationship soon after, and the couple married in 2015.