Allah's Messenger (ﷺ) said, "The most awful name in Allah's sight on the Day of Resurrection, will be (that of) a man calling himself Malik Al-Amlak (the king of kings).
Sahih al-Bukhari Book 78, Hadith 229
← Previous Hadith The most beloved names to `Ali was Abu Turab, and he used to be pleased when we called him by it, for none named him Abu Turab (for the first time), but the Prophet. Once `Ali got angry with (his wife) Fatima, and went out (of his house) and slept near a wall in the mosque. The Prophet (ﷺ) came searching for him, and someone said, "He is there, Lying near the wall." The Prophet (ﷺ) came to him while his (`Ali's) back was covered with dust. The Prophet (ﷺ) started removing the dust from his back, saying, "Get up, O Abu Turab!"

Sahih al-Bukhari Book 78, Hadith 228 Next Hadith → The Prophet (ﷺ) said, "The most awful (meanest) name in Allah's sight." Sufyan said more than once, "The most awful (meanest) name in Allah's sight is (that of) a man calling himself king of kings." Sufyan said, "Somebody else (i.e. other than Abu Az-Zinad, a sub-narrator) says: What is meant by 'The king of kings' is 'Shahan Shah.,"

Sahih al-Bukhari Book 78, Hadith 230