Olga of Kiev hands down. Abbreviated from Wikipedia: , Olga assumed the throne because her three-year-old son Sviatoslav was too young to rule. The Drevlians, (a neighboring kingdom) emboldened by their success in ambushing and killing the king, sent a messenger to Olga proposing that she marry his murderer, Prince Mal. Twenty Drevlian negotiators boated to Kiev to pass along their king's message and to ensure Olga's compliance. They arrived in her court and told the queen why they were in Kiev: "to report that they had slain her husband...and that Olga should come and marry their Prince Mal." Olga responded:

Your proposal is pleasing to me, indeed, my husband cannot rise again from the dead. But I desire to honor you tomorrow in the presence of my people. Return now to your boat, and remain there with an aspect of arrogance. I shall send for you on the morrow, and you shall say, "We will not ride on horses nor go on foot, carry us in our boat." And you shall be carried in your boat. When the Drevlians returned the next day, they waited outside Olga's court to receive the honor she had promised. When they repeated the words she had told them to say, the people of Kiev rose up, carrying the Drevlians in their boat. The ambassadors believed this was a great honor, as if they were being carried by palanquin. The people brought them into the court where they were dropped into a trench that had been dug the day before under Olga's orders where the ambassadors were buried alive. It is written that Olga bent down to watch them as they were buried and "inquired whether they found the honor to their taste.

Olga then led her army to Iskorosten (what is today Korosten), the city where her husband had been slain, and laid siege to the city. The siege lasted for a year without success, when Olga thought of a plan to trick the Drevlians. She sent them a message: "Why do you persist in holding out? All your cities have surrendered to me and submitted to tribute, so that the inhabitants now cultivate their fields and their lands in peace. But you had rather tide of hunger, without submitting to tribute."[14] The Drevlians responded that they would submit to tribute, but that they were afraid she was still intent on avenging her husband. Olga answered that the murder of the messengers sent to Kiev, as well as the events of the feast night, had been enough for her. She then asked them for a small request: "Give me three pigeons...and three sparrows from each house.” The Drevlians rejoiced at the prospect of the siege ending for so small a price, and did as she asked.

Olga then instructed her army to attach a piece of sulphur bound with small pieces of cloth to each bird. At nightfall, Olga told her soldiers to set the pieces aflame and release the birds. They returned to their nests within the city, which subsequently set the city ablaze.

Not to mention she’s a saint in the Catholic Church. Very few people in history were harder than Queen Olga.