He made a name for himself in his older brother director Ryoo Seung-wan's eclectic films, notably Die Bad (his acting debut in 2000), Arahan (2004), Crying Fist (2005), The Unjust (2010), and The Berlin File (2013).

Known for his manic energy, casual demeanor and subtle ability to command a scene, over the years Ryoo Seung-bum has cemented his status as one of Korea's top actors.

In strikingly diverse styles but with a common narrative, these shorts were re-edited, combined and released in 2000 as Ryoo Seung-wan's feature directorial debut Die Bad.

Critically acclaimed as powerfully visceral, gut-wrenching, and searingly angry, the film became an instant cult hit, earning attention for the Ryoo brothers.

[6] Ryoo next starred in Yim Soon-rye's Waikiki Brothers, a 2001 film chronicling the fate of a shoddy nightclub band, with its bittersweet mixture of boyhood aspirations and the love of music, and the despair and reality of adulthood.

[7] Later that year, he ventured into television, as part of the main cast of 50-episode family drama Wonderful Days, along with Ji Sung, Park Sun-young, and Gong Hyo-jin.

Ryoo joined Jung, Shin Ha-kyun and an ensemble cast of Jang Jin regulars in No Comment (also known as Mudjima Family), an omnibus made of three short films.

He then reunited with Noh Hee-kyung, the writer of Wonderful Days, in the TV drama Solitude, a May–December romance between a man in his early twenties and a much older single mother who is also terminally ill (played by Lee Mi-sook).

Conduct Zero capped Ryoo's year, in his first big screen leading role as the tough, fists-over-brains "king" of his high school who unexpectedly and awkwardly falls for a nerdy girl (played by Lim Eun-kyung).

In Min Kyu-dong's short Secrets and Lies (released by the Korean Academy of Film Arts in the 2003 omnibus Twentidentity), Ryoo's character finds himself in a dilemma when his fiancee's mother hits on him.

Only at the climax would the two protagonists meet as opponents in the final match, two men from different backgrounds and social positions, but united in their status as total losers, struggling to regain self-respect and purpose in their lives.

[25] Crying Fist opened against A Bittersweet Life, and despite excellent reviews for both films, they ended up canceling each other out at the box office, selling a little over a million tickets each.

In 2006, his real-life ex-girlfriend Gong Hyo-jin asked him to make a cameo appearance in Kim Tae-yong's critically acclaimed drama Family Ties.

Ryoo and Im Chang-jung lent their voices to the adult animated comedy Aachi & Ssipak, set in a futuristic world fueled by human feces where the government implants a microchip into each of its citizens' anuses to check their bowel movements for stable energy supply, rewarding good performance with addictive popsicles.

He played a teacher assigned to a mountainous village, but who gets trapped in the middle of nowhere for three months, unable to move his right foot after stepping on a land mine; reviews called his cameo appearance "hilarious.

The show's success also attracts the attention of the Japanese colonial government, and one of his voice actors is secretly working for the Korean Independence Army.

The spy action film/parody is set during the 1940s in the last years of Japanese colonial rule, as Dachimawa Lee, his allies and enemies search for the whereabouts of a stolen national treasure, a golden Buddha statue that also contains a list of Korean freedom fighters wanted by imperial authorities.

[51] Co-starring Kim Joo-hyuk and Jo Yeo-jeong, the costume drama depicted the Joseon era's sexual mores and class system with sly humor and cynicism.

[52][53][54] Ensemble comedy Foxy Festival explored unconventional sexual preferences in a light-hearted and non-judgmental manner, and in it Ryoo played a fish sausage ("odeng") hawker with a RealDoll fetish.

"[59] For Ryoo's stunningly accurate portrayal of the arrogance, rudeness and weariness of stereotypical Korean middle-aged men in positions of power,[60] he won Best Actor at the Buil Film Awards and the Fantasia Festival in Canada.

"[62][63] Ryoo played a zombie in Yim Pil-sung's short film A Brave New World, part of the science fiction omnibus Doomsday Book.

Ryoo was a scene stealer in the role of a daft character who fakes his own death in order to hide from loan sharks and collect his insurance money, but stumbles into two researchers attempting to steal a corpse with an embedded computer chip containing stolen technology.

He said it was his first time to portray self-sacrificing love,[69] and director Bang Eun-jin commended the maturity in his acting when she instructed him "to cry with your heart, not with the face.

"[70] He was cast in a supporting role in The Berlin File, Ryoo Seung-wan's 2013 spy thriller also starring Ha Jung-woo, Han Suk-kyu, and Jun Ji-hyun.

Ryoo returned to acting in 2015 with a leading role in Im Sang-soo's Intimate Enemies, a thriller about four people who find bags of money at a car crash site and decide to use it to mete out revenge against corrupt corporations.