Emperor Hirohito (April 29th, 1901 - January 7th, 1989) was the 124th Emperor of Japan, reigning from December 1926 to his death in 1989. During the first years of his rule, he was informed of a revolt and immediately ordered that it be put down, referring to the officers as "rebels" (bōto). Shortly thereafter, he ordered Army Minister Yoshiyuki Kawashima to suppress the rebellion within the hour, and he asked for reports from Honjō every thirty minutes. The next day, when told by Honjō that little progress was being made by the high command in quashing the rebels, the Emperor told him "I Myself, will lead the Konoe Division and subdue them." The rebellion was suppressed following his orders on February 29. After World War II he put his uncle Naruhiko Higashikuni as prime minister. Various leaders attempted various times to put him on trial for war crimes.
He was known for his hatred towards other Asian groups, some estimate he may have been the mastermind behind the death of 10,000,000 Asians. He particularly enjoyed impaling them with sharp pieces of bamboo and with swords. His forces also forced prisoners to watch their families being raped and even forced men to rape their daughters. While his regime would calm down over the years, many consider him to be one of the most brutal dictators in all of recorded history.
Although World War 2 was real life and not fictional, you could consider him as the quaternary antagonist with Adolf Hitler being the primary antagonist, Benito Mussolini being the secondary antagonist, and Francisco Franco being the tertiary antagonist.
Emperor Hirohito on Real-life Heroes and Good Guys Wiki