In at least two Star Trek episodes, a "Lee Kuan" is mentioned in the same breath as very well-known imperialists (Alexander, Caesar, Hitler, to name a few). One episode is Season 3, Episode 14 (Whom Gods Destroy), and the previous one is Season 2, Episode 21 (Patterns of Force). Googling leads me to Lee Kuan Yew, who was leader of Singapore during that time. But Lee Kuan Yew doesn't seem to be like Alexander, Caesar or Hitler, in that there seems to be no imperialistic aggression towards other nations (looking at the Wikipedia article on Military history of Singapore). So who is this Lee Kuan? Is he fictional?
Remember that Star Trek takes place in the future and not everyone mentioned has existed. If you ever have questions, I strongly encourage you to check out Memory Alpha, the Star Trek Wikia.
From Memory Alpha Wikia (information from direct Star Trek canon):
Lee Kuan was a noted Human historical political despot on Earth sometime between the mid-20th and the 23rd century, who ultimately failed at his goals of conquest and absolute power.
Spock put him in one line with Ramses, Julius Caesar, Alexander, Napoléon Bonaparte, and Hitler to show that Earth history is full of men seeking absolute power. (TOS: "Patterns of Force")
Fleet Captain Garth of Izar boasted to Captain James T. Kirk that as Master of the Universe, he would go much farther and have more success than other previous despots such as Lee Kuan, Alexander, Caesar, Napoléon, Hitler, and Krotus. (TOS: "Whom Gods Destroy")
From Memory Beta Wikia (information from licensed Star Trek works):
Lee Kuan was a noted Human historical political despot on Earth during the early-to-mid 21st Century, who ultimately failed at his goals of conquest and absolute power.
In the year 2031, Kuan helped to strengthen the Eastern Coalition (also known as the ECON), an alliance of Asian nations politically opposed to the United States and its allies. By 2051, Kuan held the rank of general in the ECON armed forces, at which point he overthrew the emerging democracy. He launched an attack on the Americas, joined by the Pacific nations.