Krotus was a noted historical despot who, in the opinion of Fleet Captain Garth of Izar, failed to achieve Garth's ideal of ultimate conquest.
"Lord" Garth boasted to Captain James T. Kirk that as "Master of the Universe," he would go much farther and have more success then other previous rulers such as Alexander the Great, Caesar, Napoléon Bonaparte, Adolf Hitler, Lee Kuan, and Krotus. (TOS: "Whom Gods Destroy")
Apocrypha
According to the RPG manual Among the Clans, Krotus was the Ka'Thelan Conqueror of Andoria, who swept across the planet, forcing the Andorians into a new cultural and technological era. His entire world bowed to him, but his empire ultimately crumbled and he was murdered by his own daughter.
This information is further referenced by Michael A. Martin in his Pocket ENT novel, Beneath the Raptor's Wing.