Hadithcore
Sahih al-Bukhari, 6206
sahih

Narrated Abu Huraira:

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.,"

حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، رِوَايَةً قَالَ ‏

‏ أَخْنَعُ اسْمٍ عِنْدَ اللَّهِ ـ وَقَالَ سُفْيَانُ غَيْرَ مَرَّةٍ أَخْنَعُ الأَسْمَاءِ عِنْدَ اللَّهِ ـ رَجُلٌ تَسَمَّى بِمَلِكِ الأَمْلاَكِ ‏

‏‏.‏ قَالَ سُفْيَانُ يَقُولُ غَيْرُهُ تَفْسِيرُهُ شَاهَانْ شَاهْ‏.‏

References2 variants
In-Book Reference
Book 78, Hadith 230
USC-MSA web (English) reference
Vol. 8, Book 73, Hadith 225 (deprecated numbering scheme)