In another universe, Benedict Cumberbatch played the villain in Thor: The Dark World
The Doctor Strange In The Multiverse Of Madness actor was offered the role of Malekith, but decided to wait for a part that was "a bit more juicy"

Throughout the Marvel Cinematic Universe’s existence, casting ‘what ifs’ have always been a fun look at a how differently these movies and characters could have gone. Before he was Earth-838's string-cheesed Reed Richards, John Krasinski auditioned for everyone’s favorite Boy Scout, Captain America. Even his wife Emily Blunt was nearly the MCU’s Black Widow in Iron Man 2 before turning down the role due to scheduling conflicts.
The multiverse is vast, and it seems that another casting possibility would have given us a very different Doctor Strange. Though he currently pulls off the grey side streaks and Cloak of Levitation in Doctor Strange In The Multiverse Of Madness, Benedict Cumberbatch revealed in a recent interview with BBC Radio 1 that he almost played Malekith, the villain in Thor: The Dark World.