Multiple realities(covers information from several alternate timelines)
A tyrant was the ruler of a political entity or specific area who ruled without constraints and oppressive towards his subjects.
In Klingon mythology, Molor was sometimes described as a tyrant. (TNG: "Rightful Heir", "Firstborn")
The 19th century song A British Tar featured the line "...or the tang of a tyrant tongue!" (Star Trek: Insurrection)
During the Eugenics Wars on Earth in the 1990s, a series of Augment tyrants ruled over several areas. Khan Noonien Singh was described as "the best of the tyrants" and was the last one to be overthrown. (TOS: "Space Seed")
On Sarpeidon, Zor Kahn had the epithet "the Tyrant". (TOS: "All Our Yesterdays")
In 2370, Kubus Oak claimed he had never liked the "arrogant tyrant" Gul Dukat, even though the two had worked closely together during the occupation of Bajor. (DS9: "The Collaborator")
In 2372, Julian Bashir described Kira Nerys as a "vile little tyrant". (DS9: "Shattered Mirror")