League of Legends professionals are mostly very young and many don't stick with esports as competitive players for too long. Generally speaking, these players retire in their mid to late 20s and take alternative career paths within their niche. Many become coaches, team owners, streamers, commentators, or something similar. Just look at Phreak, Kobe, Saintvicious, Jatt, and many others for evidence.
Since their retirement announcements tend to come suddenly, those who don't follow the esports up close might only find out about it when the player appears doing something else professionally. Although they're not actively participating in team fights or trying to solo Baron, they left their own esports history and legacies (for better or worse).
10 HotshotGG - George Georgallidis
When taking a break from college, Goerge "HotShotGG" Georgallidis decided to play League of Legends. The sudden desire to try out the game came after playing DotA -- a game that made him realize he liked the MOBA genre. HotShotGG soon grew to be one of the best League of Legends players in the world which caused him to drop out of college in order to become a professional player.
He founded the Counter Logic Gaming team (more commonly known as CLG) -- a team that placed 5th in the Riot Season 1 Championship back when items like Leviathan still existed. The last time we saw George in action was in 2014; currently, he is a retired esports player who is focused on managing his team.
9 xPeke - Enrique Cedeño Martínez
The former owner of team Origens, Enrique "xPeke" Cedeño Martínez used to be a feared mid-laner in Fnatic. His favorite champions were Kassadin, Ahri, LeBlanc, Orianna, and Zed - one of the most banned champions ever. The last time that Enrique Cedeño was seen on the mid lane professionally was back in 2015.
This player is mostly known for one of the most famous plays in League history. He managed to backdoor a nexus with his Kassadin during a thrilling 1v2 situation. Since then, because the LCS picture-in-picture camera would many times show split pushes and backdoors, it started being called "the Peke Cam."
8 Reginald - Andy Dinh
Andy Dinh is an esports player who managed to get the first Pentakill in competitive play with his Gragas. As a player and a coach, Reginald is known for his temper which eventually led to him being nicknamed Rageinald.
At first, his playstyle was very aligned with his known temper. He was constantly playing aggressively and looking for kills, but he only improved during his days as a professional mid laner. Curiously, the name "Reginald" was just Andy's attempt to come up with the most annoying name possible for someone to have.
7 ocelote - Carlos Rodríguez Santiago
Carlos Rodríguez Santiago is known for his many scarves, his mean Cassiopeia, and for his past as a professional World of Warcraft player. He used to play under the name "ocelote" and he does not capitalize the first letter of that name because he believes that all letters of his name are equally important.
Although he started playing League of Legends during its beta stages, he did not stick for long as a pro player. At first, ocelote became a star when he was playing for SK Gaming, but eventually founded his team: Gamers2. He was banned twice throughout his career because of his toxic behavior during games (a long-running issue in the LoL community). With time, Carlos has taken steps to change his behavior.
6 DoubleLift - Yiliang "Peter" Peng (彭亦亮)
Once considered the most well-known North American player, Yiliang "Peter" Peng played for CLG, TSM, and Team Liquid. Although he was primarily known for being amazing with Blitzcrank, Poppy, and Lee Sin, it was his bot lane performance that made him the amazing player he became. As an AD Carry, he was one of the best in his region, but certain things have always held him back.
For instance, Doublelift is known for constantly trash-talking his opponents. He even has his own catchphrase: "everyone else is trash" which made him very entertaining for fans of the esport. Many were sad to see him separated from his long-time bot-lane partner Zaqueri "ahpromoo" Black. He remains an active player for Team Dignitas (DIG). As of March 9, 2021, Doublelift did "rejoin" TSM as a streamer, but (so far) he has no indicated that he will compete again.
5 Bjergsen - Søren Bjerg
Once a fresh-faced, eager mid laner for TSM, Søren "Bjergsen" Bjerg was declared one of the best mid laners among those who played in the NA LCS. He was the second player to move from the EU LCS to the NA LCS. Over the course of his career, he won six LCS titles and participated in five world championships with the same team.
Bjergsen is also known for being the first European player to become a start in North America. He scored the first pentakill ever in the EU LCS with his Syndra -- a champion he used to pick since before she was even seen as meta. His champion pool is as deep as the Marianas Trench and he put the entire team on his back many a time.
4 Snoopeh - Stephen Ellis
Like many other competitive players, Stephen "Snoopeh" Ellis bounced around a bit during his relatively brief career. His break into stardom happened when he signed with CLG EU in 2011, but he made a name for himself under Evil Geniuses (EG). In contrast to aggro-junglers, Snoopeh took a more support-based approach, but still ganked fairly often.
He left the competitive scene in 2014, but many fans still reminisce about his impact on the EU sector. Snoopeh's former teammate Krepo recently announced his return to the LoL scene recently, too. However, in Snoopeh's case, it seems that he has fully moved onto other ventures.
3 MadLife - Hong Min-gi (홍민기)
Hong "MadLife" Min-gi was once considered one of the best players ever of League of Legends and is currently a streamer for Hanwha Life Esports. And although he is not among the funniest League of Legends streamers, he is very entertaining. He started playing Starcraft when he was 7 and moved towards the MOBA genre eventually.
Because of his legendary skills, people used to say that the MiG on his tag didn't stand for the name of the team (Maximum Impact Game) but for Madlife is God. Unlike many esports athletes, he prefers to be called by his full name, Hong Min-gi, instead of by MadLife.
2 Score - Go Dong-bin (고동빈)
Previously known as Joker, Go "Score" Dong-bin is one of the greatest junglers ever seen in League of Legends. Although he was a jungler, his favorite champions were Corki and Ezreal. The latter called a lot of attention to him due to his amazing positioning.
Score was afflicted by the "second place curse" as it was generally called. This became a meme because, for many years when competing in the LCK, Score would end in second. Luckily for him, the curse was broken in 2018. After that moment of hard-earned success, the player retired in 2019.
1 Uzi - Jian Zi-Hao (简自豪)
An amazing AD Carry player, often due to his outstanding mechanical skills, Jian "Uzi" Zi-Hao has one of the longest careers in League of Legends. Uzi played the game for 8 years and only stopped due to wrist injuries. The official announcement of his retirement was made last year.
One of the things that prove his mechanical superiority in the game is the fact that he held the highest CS/M throughout every season of LPL that he was in since 2015. He also managed to get five pentakills in LPL games. However, though he was a remarkable player, he has had attitude and discipline issues like many professional League players.