More in the spirit of the OP, the winner is Beria, Stalin’s secret police chief. Someplace in this pile of books, I have a copy of Inside the Court of the Red Tsar. It seems that Beria not only authorized the killing of the Polish elites in '39, he also took part.
It seems he and a couple of other guys spent over a week doing it. A group of fifty or so people were led in. Beria and his buddies would kill them with pistols and then they went in the next room to drink while the killing room was cleaned up.
The book gave some guess as to how many it totaled to, and I do not have that figure at hand, still it was thousands.
Beria died soon after Stalin did, on his knees begging.
If we’re defying the OP and including aerial weaponry, I’d say Erich Hartmann is clearly trumped by countryman Hans-Ulrich Rudel, a Ju-87 pilot, who is credited with destroying over TWO THOUSAND Soviet tanks, trucks and other vehicles, plus a Soviet battleship, Marat. I’d bet he killed more than 500 people.
The difficulty is finding reliable sources:
*
When David returned from the slaughter of the Philistine, the women came out of all the cities of Israel, singing and dancing, to meet King Saul, with timbrels, with songs of joy, and with instruments of music. And the women sang to one another as they made merry.
"Saul has slain his thousands
And David his ten thousands"
And Saul was very angry, and this saying displeased him; he said “They have ascribed to David ten thousands, and to me they have ascribed but thousands…” And Saul eyed David from that day on.*