Warning: The following contains SPOILERS for Harley Quinn season 2, episode 4, "Thawing Hearts."
DC Universe's Harley Quinn season 2, episode 4, "Thawing Hearts", revealed that Kite Man's nemesis is the one supervillain with an even stupider gimmick than himself; the uncanny Condiment King. This revelation led to an absurdly pathetic battle, in which Condiment King attempted to ruin Kite Man's wedding to Poison Ivy in the lamest way possible.
Created by Bruce Timm, Paul Dini and Randy Rogel, Condiment King first appeared in the Batman The Animated Series episode "Make 'Em Laugh." Apprehended after a failed restaurant robbery and unmasked as popular comedian Buddy Standler, he was eventually proven to be a victim of a plot by The Joker. One year earlier, The Joker, disguised as a comedian called Smilin' Shecky Rimshot, had entered a contest to find the funniest comedian in Gotham City and was promptly run off the stage by Standler and the other celebrity comedians judging the contest. This led The Joker to steal the mind control technology of The Mad Hatter and use it to make fools of the judges by turning them into ridiculous supervillains.
Like Harley Quinn herself, Condiment King later made the leap from cartoons to comics; this time as a "serious" villain. Chuck Dixon and Scott Beatty introduced Condiment King into the DC Comics universe in the Batgirl: Year One mini-series, where he was a loser with the unlikely name of Mitchell Mayo. This version of the Condiment King was no more successful in his serious attempts at villainy than the comedic version from the cartoons and was unceremoniously beaten to death with his own ketchup cannon in the pages of Final Crisis. Harley Quinn season 2, episode 4 introduces Condiment King as a "legitimate" supervillain and a rival of Chuck "Kite Man" Brown, though his villainy seems largely limited to posting passive-aggressive comments on Kite Man's social media and sarcastic congratulations on his engagement to Poison Ivy in a text.
It is only later in the Harley Quinn episode that Condiment King unveils his sinister scheme to ruin the wedding by securing Kite Man's dream wedding venue for his own hastily thrown-together nuptials to a woman named Becca. The two rivals butt heads at the Old Gotham Corn Factory, where Condiment King reveals his plot and stains Kite Man's suit just before he meets the fastidious manager responsible for deciding which of them will win the last free weekend this year for their wedding.
While this clash of the Titans is far closer in scope to the feud between Jerry and Newman on Seinfeld than Batman and The Joker, both Mitchell and Chuck regard their rivalry with deadly seriousness. Still, when push comes to shove, Kite Man abandons his appointment and his dream to help Ivy when she is called upon to help Harley Quinn in her latest scheme. This speaks well of their relationship and suggests that while Kite Man may have lost a battle, he's won the war in proving his worth to the woman he loves.