The BBC adaptation of Arthur Conan Doyle's eponymous detective, Sherlock, features a diverse range of villains, varying from brilliant to bizarre. The modernized adaptation stars Benedict Cumberbatch as Sherlock Holmes and Martin Freeman as Dr. John Watson, with impressive guest stars also bolstering the series.

Among the villains, Lord Moran is arguably the worst, as he appears only briefly in season 3, episode 1, "The Empty Hearse," and is quickly defeated by Sherlock. Dr. Bob Frankland, who is revealed as a villain in season 2, episode 2, "The Hounds of Baskerville," is underwhelming compared to the grandeur of the hallucinated hounds he creates.

Jonathan Small, also known as the Mayfly Man, is a minor villain in season 3, episode 2, "The Sign of Three," with a slightly underdeveloped character, despite displaying cruelty and cunning. The Golem, who pursues Sherlock in season 1, episode 3, "The Great Game," is incredibly unnerving but does not feature extensively in the episode.

Charles Augustus Magnussen, played by Lars Mikkelsen, is an unsettling media mogul preoccupied with determining "pressure points" to blackmail his victims. Culverton Smith, portrayed by Toby Jones, is a frightening and innovative killer in season 4, episode 2, "The Lying Detective," but is slightly overshadowed by other plot points.

Jeff Hope, the first villain to appear in Sherlock, is portrayed by Phil Davis and is particularly terrifying, coming close to killing Sherlock and displaying a palpable relish for murder. Eurus Holmes, featured most prominently in season 4, episode 3, "The Final Problem," offers a pervasive villainous presence, played with chilling elegance by Sian Brooke.

Irene Adler, portrayed by Lara Pulver, charms Sherlock himself in season 2, episode 2, "A Scandal in Belgravia," with impressive levels of planning and preparation. Jim Moriarty, portrayed by Andrew Scott, is undoubtedly the greatest villain depicted in Sherlock, with his enigmatic persona and spellbinding performance captivating audiences.