The Mangekyo Sharingan is the evolved form of the Sharingan which is awakened when the user suffers a trauma from the loss of a loved one. After the evolution, the Sharingan changes its pattern, which is exclusive to the user.
Here’s how each weilder of the Mangekyō Sharingan awakened it.
9. Fugaku Uchiha
Fugaku Uchiha was a weilder of the Mangekyō Sharingan, according to Itachi Shinden and the anime. He kept his Mangekyō Sharingan a Secret from everyone because he feared they would force him to control the Nine Tails.
Apparently, he awakened it in the Third Great Ninja War, where he witnessed the death of his comrade, who gave his life to save him.
8. Indra Ōtsutsuki
Indra Ōtsutsuki was the son of the Sage of Six Paths. He was a weilder of the Sharingan, as he inherited the Physical Prowess of his father. He managed to awaken the Mangekyō Sharingan too. In the anime, he achieved this by killing two of his close friends, in order to gain power to fight his brother, Asura. In the manga, it is unknown how he achieved this feat.