Messenger of Allah 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).  

قَالَ رَسُولُ اللَّهِ ﷺ أَخْنَى الأَسْمَاءِ يَوْمَ الْقِيَامَةِ عِنْدَ اللَّهِ رَجُلٌ تَسَمَّى مَلِكَ الأَمْلاَكِ  

The vilest names in Allah’s sight on the Day of resurrection will be that of a man called Malik al-Amlak. Abu Dawud said: This tradition has also been transmitted by Shu'aib b. Abi Hamzah from Abi al-Zinad through different chain of narrators. This version has the words "akhna' ismin" (most obscene name) instead of "akhna ismin" (the vilest name).  

النَّبِيَّ ﷺ قَالَ أَخْنَعُ اسْمٍ عِنْدَ اللَّهِ تَبَارَكَ وَتَعَالَى يَوْمَ الْقِيَامَةِ رَجُلٌ تَسَمَّى مَلِكَ الأَمْلاَكِ  

The vilest names in Allah’s sight on the Day of resurrection will be that of a man called Malik al-Amlak. Abu Dawud said: This tradition has also been transmitted by Shu'aib b. Abi Hamzah from Abi al-Zinad through different chain of narrators. This version has the words "akhna' ismin" (most obscene name) instead of "akhna ismin" (the vilest name). (Using translation from Abū Dāʾūd 4961)   

"أخنع الأسماءِ عند الله تعالى يوم القيامةِ رجلٌ تسمَّى "مَلِك الأملاك" لا مالكَ إلا الله ".