William Peter Hjelte (born 16 October 1994), better known by his gamer tag Leffen, is a Swedish professional fighting game player and streamer.

[4] Although recognized as one of the best players in Melee history and having a dedicated fan base, Leffen has also been considered one of the most controversial and polarizing players in Super Smash Bros. history, due in part to accusations of aggressive and anti-social behavior— which resulted in a temporary ban from the Swedish competitive Melee scene in 2013.

Prior to EVO 2014, Joe Cribari of Nintendo Enthusiast listed Leffen among the three "underdogs" with the greatest chance to win the tournament.

In VGBootCamp's Apex 2015 Salty Suite, Hjelte defeated Kashan "Chillin" Khan in a first-to-five set without dropping a single game.

On April 29, 2016, Leffen announced that his Form I-129 petition to obtain a visa had been denied by United States Citizenship and Immigration Services.

[18] However, on July 14 Leffen announced that he had run into additional delays in the visa approval process and would miss EVO.

[19] Finally, on October 3, Leffen's visa was approved, allowing him to compete in US-based tournaments again, in time for The Big House 6.

[25] Leffen is a controversial figure in the Super Smash Bros. community, where he has been accused of aggressive and toxic behavior, bullying, and poor sportsmanship, notably due to his tendency to target other players or figures of the community with insults or confrontational statements, both online and in real life; other accusations include spreading false rumors about other players, intimidating newcomers, and making fun of individuals' illnesses or disabilities.

"[27] Leffen's behavior caused him to be banned from the entire Swedish tournament scene for much of 2013, as well as from the online forum Smashboards, on which he was active.

[30] One of the officials behind the tournament ban stated that this was due to heavy bullying and overall poor treatment of fellow players, spreading false rumors about other players stealing or taking illegal drugs, making fun of others' diseases and disabilities, poor sportsmanship, trying to push people out of the community, and being "extremely mean" to his partners in Doubles if they made mistakes.

[34][33] In an April 2015 interview, Leffen justified his behavior by claiming he was trying to elevate the level of play on the Melee scene, stating "I actually do like the villain role.