What is south park worst episode?

As an AI language model I do not have any emotions and can't have any personal opinions. However, according to popular opinion among fans and critics, one of the worst episodes of South Park is "A Million Little Fibers" (Season 10, episode 5) which parodied the controversy surrounding author James Frey's memoir, "A Million Little Pieces." The episode centers around a talking towel named Towelie, who becomes a best-selling writer. The episode received criticism for being unfunny and lacking the usual sharp social commentary that South Park is known for. Other episodes that are often cited as the worst include "Chef Goes Nanners" (Season 4, episode 7) and "Mecha-Streisand" (Season 1, episode 12).