Which is the Greatest Name of Allah?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

There are many Ahadith that mentioned the greatest name of Allah some of them are as following:

Imam Tirmizi and Abu Dawood reported from Buraidah that the Apostle of Allah (peace be upon him) heard a man saying: “O Allah, I ask You, I bear witness that there is no god but You, the One, He to Whom men repair, Who has not begotten, and has not been begotten, and to Whom no one is equal, and he said: You have supplicated Allah using His Greatest Name, when asked with this name He gives, and when supplicated by this name he answers”. The chain of this Hadith is sound.

In another narration Anas said, “I was sitting with the Apostle of Allah (peace be upon him) and a man was offering prayer. He then made supplication: O Allah, I ask Thee by virtue of the fact that praise is due to Thee, there is no deity but Thou, Who showest favour and beneficence, the Originator of the Heavens and the earth, O Lord of Majesty and Splendour, O Living One, O Eternal One. The Prophet (peace be upon him) then said He has supplicated Allah using His Greatest Name, when supplicated by this name, He answers, and when asked by this name He gives”.

There is another Hadith from Asma Bint Yazeed that the Prophet (Sallallahu Alaihi wa Sallam) said: "The greatest name of Allah is in these two verses {And your Ilâh (God) is One Ilâh (God - Allâh), Lâ ilâha illa Huwa (there is none who has the right to be worshipped but He), the Most Beneficent, the Most Merciful.}[2:163] The beginning of Surah Al-Imran {Alif-Lâm-Mîm. [These letters are one of the miracles of the Qur'ân, and none but Allâh (Alone) knows their meanings]. Allâh! Lâ ilahâ illa Huwa (none has the right to be worshipped but He), the Ever Living, the One Who sustains and protects all that exists.}[3:1-2]".  This is a Hasan (acceptable) Hadith. 

Allah knows best.