What is the greatest Ayah in quran?

Answer 1

اللَّـهُ لَا إِلَـٰهَ إِلَّا هُوَ الْحَيُّ الْقَيُّومُ ۚ لَا تَأْخُذُهُ سِنَةٌ وَلَا نَوْمٌ ۚ لَّهُ مَا فِي السَّمَاوَاتِ وَمَا فِي الْأَرْضِ ۗ مَن ذَا الَّذِي يَشْفَعُ عِندَهُ إِلَّا بِإِذْنِهِ ۚ يَعْلَمُ مَا بَيْنَ أَيْدِيهِمْ وَمَا خَلْفَهُمْ ۖ وَلَا يُحِيطُونَ بِشَيْءٍ مِّنْ عِلْمِهِ إِلَّا بِمَا شَاءَ ۚ وَسِعَ كُرْسِيُّهُ السَّمَاوَاتِ وَالْأَرْضَ ۖ وَلَا يَئُودُهُ حِفْظُهُمَا ۚ وَهُوَ الْعَلِيُّ الْعَظِيمُ ﴿٢٥٥﴾

Meaning English Translation:

{Allah, there is no god except He, the Living, the Everlasting. Neither dozing, nor sleep overtakes Him. To Him belongs all that is in the heavens and the earth. Who is he that shall intercede with Him except by His permission! He knows what will be before their hands and what was behind them, and they do not comprehend anything of His Knowledge except what He willed. His Seat embraces the heavens and the earth, and the preserving of them does not weary Him. He is the High, the Great. (255)} [Quran, chapter 2, Surant Al-Baqara, verse 255]

Answer 2

To list all ayas in quran (6236 Ayas) means to write down the whole Quran which is not practical withing the answer allowed space.

Answer 3

The greats ayat in Quran is ayatul kursi (surah bakara, 255)

Answer 4

It's Ayatul Kursi.