Early career

Ruler began his playing career in 2016 when he joined Stardust of Challengers Korea, a developmental league for the League of Legends Champions Korea (LCK).^[2]

Samsung Galaxy

Ruler was signed by Samsung Galaxy (SSG) for the 2016 LCK Summer Split.^[3] SSG finished the split in fourth place in the standings. In the first round of the playoffs, SSG defeated Afreeca Freecs. Their opponents in the next round was KT Rolster, whom they lost to 0 games to 3, ending their playoff run. Accumulating 50 championship points, SSG entered the LCK regional qualifier for the 2016 World Championship. They secured the third LCK seed for Worlds by defeating KT Rolster in the finals.^[4] After advancing as the top seed from their group, SSG swept both Cloud9 and H2k-Gaming in the playoffs, earning a spot in the final against SK Telecom T1 (SKT).^[5] In the best-of five series, SKT won the first two games. After 25 minutes into in game three, SSG was losing 0–7, but four minutes later, SSG won a 3–0 fight due in part to Ruler's high damage output. Samsung went on to win the game 19–17 after 71 minutes. Following a win in game four, the match went to a decisive fifth game. Eight minutes in, Ruler killed SKT's Bae "Benji" Sung-woong after a bad invade. However, SSG ultimately lost the game 8–13, finishing Worlds in second place.^[6]

After securing third- and fourth-place finishes in the 2017 LCK Spring and Summer splits, respectively, SSG qualified for the 2017 League of Legends World Championship.^[7] In the World Championship group stage, Samsung finished with a 4–2 record, with both losses coming from Royal Never Give Up.^[8] Progressing to the knockouts, they defeated Longzhu Gaming and Team WE in the quarterfinals and semifinals, respectively, SSG advance to the World Championship finals, where they once again faced SK Telecom T1.^[7] In game one of the final, Ruler played Xayah and had no deaths and 100% kill participation, contributing two kills and five assists. This trend continued in the second game, playing as Xayah, he maintained zero deaths, four kills, and five assists.^[8] Switching to Varus in the third game, a pivotal moment occurred at the 39-minute mark, when Ruler used a move called Flash, propelling himself toward SKT mid laner Lee "Faker" Sang-hyeok, creating a chaotic situation. However, SKT's players were positioned in a way that created a brief opening, and Ruler took advantage of the opportunity and killed Faker. Although this left Ruler exposed to attack, Jo "CoreJJ" Yong-in used all of his abilities to keep Ruler alive, and with a miscalculated attack by SKT's Kang "Blank" Sun-gu, Ruler survived.^[9] While falling just short of 100% kill participation in the third game, Ruler concluded with four kills, two deaths, and 11 assists. With a 3-game-to-0 series victory, Ruler won his first World Championship. Throughout the series, Ruler adeptly managed minion waves, secured kills, and contributed to tower takedowns. Despite occasional mistakes, Ruler's team collaborated effectively to rectify them, and Ruler earned the MVP title for the series.^[8][10]

Gen.G

In November 2017, KSV Esports, later rebranded as Gen.G in May 2018, acquired the roster of Samsung Galaxy.^[1][11] The team finished with a 9–9 record, securing qualification for the 2018 LCK Spring playoffs. However, they faced an early exit in the first round, losing to SK Telecom T1.^[12][13] In the subsequent summer split, Gen.G finished with a 13–5 record, earning another playoff berth. Their first playoff opponent was Afreeca Freecs, and despite their efforts, Gen.G faced a 0–2 defeat, with Afreeca effectively limiting Ruler's production throughout the match.^[14][15] Following a victory against Kingzone DragonX in the 2018 LCK regional qualifier finals, Ruler and the team qualified for the 2018 World Championship. However, they were unable to advance beyond the group stage, marking the end of their journey in the tournament.^[16] However, the team was eliminated in the group stage.^[17]

Gen.G struggled throughout the 2019 LCK season. They finished the spring split in seventh place with a 5–13 record, followed by a sixth-place finish in the summer with a 10–8 record. They failed to reach the playoffs in either split. In a 2022 interview, Ruler expressed that the 2019 season marked the most challenging period in his career as a player. During this time, he contemplated the possibility of retirement.^[18]

Following a challenging year, Gen.G made significant changes by releasing eight of their ten players. However, they retained Ruler, signing him to a three-year contract extension on September 22, 2019. The team built their 2020 roster around Ruler, who played a pivotal role in attracting top free agent Kim "Clid" Tae-min to join the team in the offseason.^[19] On April 1, 2020, during a match against T1, Ruler achieved a milestone by becoming the 11th player in LCK history to secure 1,000 kills.^[20] Gen.G performed well in the regular season, finishing atop the standings with a 14–4 record and advancing directly to the 2020 LCK Spring Finals. Despite a strong regular season, Gen.G faced T1 in the final but lost by a score of 0–3.^[21] In the summer split, Gen.G maintained their momentum with another 14–4 record, securing a third-place standing.^[22] Ruler's performance throughout the season earned him a spot on the 2020 Summer LCK First All-Pro team.^[23] During the playoffs, the team reached the semifinals but were defeated by DRX.^[24] To qualify for the 2020 World Championship, Gen.G competed in the LCK regional qualifiers, making it to the final against T1. Ruler's contributions, including playing as Senna in the first match and Ezreal in the second with a quadra-kill late in the game, helped secure victories. Gen.G went on to win the third match and clinched the third LCK seed for the World Championship.^[25] The team advanced past the group stage of the event and faced G2 Esports in the quarterfinals. After losing the first game, Gen.G got off to a quick start in game two, with Ruler getting a double kill right after Martin "Wunder" Nordahl Hansen claimed first blood. However, G2 quickly took over and won the game. The team showed signs of life in game three, with Ruler visibly trying to bring the match to a fourth game. However, G2 won the game and the match, ending Gen.G's run.^[26][27]

In the 2021 LCK Spring Split regular season, Gen.G secured a second-place finish with a 13–5 record.^[28] Ruler was named to the 2021 Spring LCK First All-Pro team, leading all bot laners in damage per minute, KDA, and gold per minute. Additionally, he led in damage share, with an average contribution of 31.3% to Gen.G's overall damage per game.^[29] Despite their impressive regular-season performance, Gen.G fell short in the playoff final, losing to DWG KIA.^[30] In the subsequent summer split, Gen.G continued their solid performance, finishing in second place with a 12–6 record. While they lost to T1 in the playoff semifinals, the team had already secured qualification for the 2021 World Championship, marking Ruler's fifth appearance.^[29] While the team successfully advanced out of the group stage and into the knockouts, Gen.G fell to EDward Gaming in the semifinals.^[31]

In the 2022 LCK Spring Split, Gen.G finished with a 15–3 record.^[32] They reached the 2022 LCK Spring Finals but were defeated by T1 with a score of 1–3.^[33] In July 2022, during a match against Liiv Sandbox in the 2022 Summer Split, Ruler achieved his 2,000th kill in the LCK, becoming the third player in LCK history to reach this milestone, behind Lee "Faker" Sang-hyeok and Kim "Deft" Hyuk-kyu.^[34] During the 2022 LCK Summer Split, Gen.G performed well with a 17–1 record, becoming the third team in LCK history to win 17 or more matches in a single split. Moreover, the team had an 87.5% game record record — the highest percentage in LCK history. Ruler was named the MVP of the 2022 LCK Summer Split, earning 21 of the 40 first-place votes cast by LCK commentators, players, coaches, and affiliated media members. He had the highest KDA among all LCK players at 7.6 and tied Liiv Sandbox's Lee "Prince" Chae-hwan for the most kills at 213. He was also tied with Prince for the most "Player of the Game" awards.^[35] Ruler, along with three of his teammates, earned a spot on the 2022 Summer LCK All-Pro First Team.^[36] Gen.G secured a spot in the 2022 LCK Summer Finals, where they faced T1 on August 28. In the first game, Ruler had 16 kills, contributing to Gen.G's victory with a final kill score of 19 to 6. The team went on to win the series 3–0, granting Ruler his first LCK title and securing Gen.G the top LCK seed in the 2022 World Championship.^[37] In the World Championship, Gen.G advanced past the group stage and faced DWG KIA in the knockout quarterfinals. Gen.G won the first two games of the match, but DWG came back to win the following two, bringing the match to a decisive fifth game. Late into game five, the game was tied. In the final teamfight, Ruler secured a game-winning quadra-kill, pushing Gen.G to the win and advancing them to the semifinals.^[38] They faced DRX in the semifinals, a team they had not lost to all year. However, DRX won the match, 3 games to 1, ending Gen.G's Worlds run.^[39]

On November 10, 2022, Ruler mutually parted ways with Gen.G.^[40] Following his departure, Gen.G retired Ruler's uniform number 1.^[41]

JD Gaming

Ruler joined JD Gaming (JDG) of the Chinese League of Legends Pro League (LPL) for the 2023 season.^[42] In his debut LPL match on January 14, 2023, against Bilibili Gaming, Ruler achieved a pentakill, marking his seventh in his career. The play involved Ruler initiating the skirmish by eliminating top laner Bin. Subsequently, he cornered the support player, ON, near his team's inhibitor, securing the fifth kill for the pentakill. ON conceded to Ruler in a gesture of sportsmanship.^[43] Ruler's performance throughout the regular season earned him a spot on the 2023 Spring LPL First All-Pro Team.^[44] In the playoffs, JDG reached the 2023 LPL Spring Split Final, where they faced Bilibili Gaming. JDG won the match, 3 games to 0, earning Ruler his first LPL title. Throughout the series, Ruler contributed with 19 kills, 4 deaths, and 26 assists, and was named the MVP of the finals.^[45] In the 2023 Mid-Season Invitational, JDG won their upper bracket quarterfinals against Bilibili Gaming on May 14. Ruler played a pivotal role, securing 10 kills in game one and 15 kills in game three, contributing to JDG's 3–0 victory.^[46] The team continued their success by defeating T1 in the upper bracket semifinals with a 3–2 score. Ruler finished the match with 28 kills and 17 assists.^[47] JDG went on to win the 2023 MSI Final against BiliBili, securing Ruler his first MSI title.^[48] At the end of the 2023 LPL Summer Split regular season, Ruler earned a spot on the 2023 Summer LPL First All-Pro Team.^[49] In the playoffs, JDG secured a 3–2 victory over LNG Esports in the 2023 LPL Summer Finals, achieving back-to-back LPL titles. With this win, JDG qualified as the top seed LPL representative in the 2023 World Championship.^[50] Having won both LPL titles, the MSI, and the 2023 Asian Games, Ruler and teammate Seo "Kanavi" Jin-hyeok had the opportunity to become the first players in history to win every event they had attended in a calendar year, should they win the 2023 World Championship.^[51] However, JDG were eliminated in the Worlds semifinals by T1, losing by a score of 1–3.^[52]

In November 2023, JDG re-signed Ruler on a two-year contract.^[53]