The name "Allah" refers to the Divine self in whom we believe, worship and know that He is the Giver of life and to whom we return. Allah Almighty is the One who truly deserves to be praised and thanked; He is the source of piety and forgiveness and to Him belong infinite praise, exaltation and reverence.
If the entire humans, since they first came to existence until the Day of Judgment, disbelieved in Allah, it will never affect or decrease anything from His Majesty, kingdom or Sovereignty. Allah Most High and Exalted is above any misconception or ignorance claimed by any ignorant or deviated human being.
Despite the fact that we live in a time when the majority of people follow their own whims and forget their Lord and the Day of Judgment, it is firm that the consequences of their actions will befall none but them since Allah is above what they are doing.
Allah Almighty says in the Qur'an,
And of the people is he who disputes about Allah without knowledge and follows every rebellious devil. It has been decreed for every devil that whoever turns to him - he will misguide him and will lead him to the punishment of the Blaze. [Qur'an 22:3-4].