This particular event took place at the beginning of last year. The Overwatch League was just a week into its first season and player Felix Lengyel -- better known as xQc of the Dallas Fuel -- had already earned himself a four-game suspension from the league and a $2000 fine. His own team even suspended him from the remainder of the season's first stage.
So what did Lengyel do to earn his punishments? He used a homophobic slur against an openly gay player in an opposing team. Lengyel was reportedly set off when the player -- Austin "Muma" Wilmot of the Outlaws -- jokingly used one of Lengyel's catch-phrases after the Outlaws beat the Fuel in a match.
Lengyel later addressed Wilmot on his own stream, verbally attacking him and taking several jabs at his sexual orientation. (I won't post the quote verbatim here, but there is a video available at the link above.)
Obviously, Blizzard wasn't cool with this, and since they own the Overwatch League, it took them no time to dole out a punishment.
Unfortunately, Lengyel didn't learn from his suspension and was in trouble again just a few months later, prompting the Fuel to part ways with him permanently.