The atheist is worse than the idolater
The idolater knows God Almighty, but he assigns some idols as partners or associates with God; while the atheist denies God; so the atheist is worse than the idolater.
The idolater and the associater (who associates some righteous men with God Almighty) will go to Hell to be there forever, as will the atheist go to Hell to be there forever like the associater or more.
The idolater and the associater (who associates some righteous men with God Almighty) will be punished in Hell forever, and no intercession will be accepted for his behalf; only because He considered some men equal to God, and so he did not esteem God as He should be esteemed when he considered some other men equal to God Almighty.
The punishment of the atheist will start immediately following his death, when devils will capture him and inflict him by various humiliating punishment and will be imprisoned in the fire of volcanoes or the fire of the core of the earth, which is the Hell of the present World.
[I saw a vision or night dream that I may tell it later on, about the punishment of atheists and idolaters following their death in the Hell of the volcanoes or the core of the earth.]
On Judgment Day the atheist will be punished in Saqar

Hell) forever, and no judgment will be done for him; because he denied the Creator: God: his Lord.
The idolater may be better than the atheist; because the idolater acknowledges God Most Gracious, while the atheist does not admit that God exists. The idolater has known God in addition to his associates or idols, while the atheist is worse because he is astray without master and without patron.
This is in the Quran 5: 72
لَقَدْ كَفَرَ الَّذِينَ قَالُواْ إِنَّ اللّهَ هُوَ الْمَسِيحُ ابْنُ مَرْيَمَ وَقَالَ الْمَسِيحُ يَا بَنِي إِسْرَائِيلَ اعْبُدُواْ اللّهَ رَبِّي وَرَبَّكُمْ إِنَّهُ مَن يُشْرِكْ بِاللّهِ فَقَدْ حَرَّمَ اللّهُ عَلَيهِ الْجَنَّةَ وَمَأْوَاهُ النَّارُ وَمَا لِلظَّالِمِينَ مِنْ أَنصَارٍ
The explanation:
(They are unbelievers who say: "God is the Christ the son of Mary",
but the Christ said: "Children of Israel, worship God: my Lord and your Lord;
surely, whoso associates [anything] with God, God has forbidden him Paradise, and his resort is the Fire;
wrong-doers will have no helpers [to save them from the chastisement."] )
eanassir
man-after-death.t35.com