Fictional Characters:
* Thanos: The Mad Titan from Marvel Comics is a strong contender. He wiped out half of all life in the universe with the Infinity Gauntlet in *Infinity War*. While he wasn't directly responsible for every death, the number is astronomically high.
* Darth Vader: As a Sith Lord and leader of the Galactic Empire, Darth Vader commanded a vast military force and was responsible for countless deaths. While we don't have an exact number, it would be massive.
* The Joker: While he doesn't necessarily kill with his own hands, the Joker's chaotic and destructive actions have resulted in countless deaths. His influence has driven many characters to violence, making it difficult to quantify his body count.
Real-Life Figures:
* Genghis Khan: The founder of the Mongol Empire is often cited as one of the deadliest figures in history. Estimates of his direct and indirect death toll range from 40 to 75 million people.
* Joseph Stalin: The dictator of the Soviet Union was responsible for the deaths of millions through purges, forced labor, and famine during his reign. Estimates of his death toll range from 20 to 60 million.
* Mao Zedong: The leader of the Chinese Communist Party during the Cultural Revolution was responsible for the deaths of millions through political persecution and famine. Estimates range from 40 to 78 million.
It's important to note: These are just a few examples, and the exact number of deaths attributed to any individual is difficult to determine with certainty. There are many other figures, both real and fictional, who could be included on a list of the deadliest.
Ultimately, the "most deadly" depends on how you define the criteria.