I would say Stalin has killed the most people. He's killed about 20 million give or take a few, but he didn't kill them with his hands yet his words.

I'd say Adam, Eve, or Satan. From a Biblical standpoint that makes sense since it was the willful disobedience by Adam and Eve, with a little help from Satan, that meant the whole human race should die at all. As the Bible says: Romans 5:12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned: 13 (For until the law sin was in the world: but sin is not imputed when there is no law. 14 Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come. 15 But not as the offence, so also is the free gift. For if through the offence of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many. 16 And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offences unto justification. 17 For if by one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.) 18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life. 19 For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous. 20 Moreover the law entered, that the offence might abound. But where sin abounded, grace did much more abound: 21 That as sin hath reigned unto death, even so might grace reign through righteousness unto eternal life by Jesus Christ our Lord. I guess it depends on one's definition of a person, I was assuming it to not simply be a synonym for human but rather to be a synonym for "entity" since it seems a more non-specific word.

Stalin. The Soviet Union appears the greatest megamurderer of all, apparently killing near 61,000,000 people. Stalin himself is responsible for almost 43,000,000 of these. Most of the deaths, perhaps around 39,000,000 are due to lethal forced labor.

Mao Zedong at over 50 million. Look him up :)

Whoever drove the plane into 9/11

Joseph Stalin

'Directly' responsible, as in killed with their own hands / 'fired the gun' / etc is very hard to say, perhaps the people who dropped the bombs on Hiroshima and Nagasaki? (I think around 60'000 deaths either both together or in one individual bombing - I can't remember off the top of my head) Stalin is responsible for the most over-all though, estimated at around 60 million : (

God.

Mao Zedong. 70 million. 30 million starved to death during a two year period of terrible economic policy called "The Great Leap Forward."

Chairman Mao (more than Stalin)

George bush & Jim Jones & Hitler

Super Mario

stalin, hitler!

President of the United States: Truman, is the single person directly responsible for the most deaths in history. Around 150,000 people killed in under an hour by the nuclear bombings on two Japanese cities. Around a million people injured. People still dying from the effects of that radiation to this day so figure could run into tens of millions.

9-30-2017 Actual numbers: http://www.nytimes.com/imagepages/2011/11/06/opinion/06atrocities_timeline.html?ref=sunday

I'd say it's a tie bwtween Russians and Chinese

Mao Zedong (49-78 million deaths) http://www.popten.net/2010/05/top-ten-most-evil-dictators-of-all-time-in-order-of-kill-count/

Cain killed 25% of the entire population of the world.

Mother Nature.

hitler