Salvation of all mankind from the greatest sin against Allah
(Shirk and Kufr i.e. polytheism and disbelief) I consider it essential to mention here some details of the greatest sin which will not be forgiven by Allah. This unpardonable sin is Shirk
Shirk implies ascribing partners to Allah or ascribing divine attributes to others besides Allah and believing that the source of power, harm and blessings comes from another besides Allah.
Almighty Allah says:
“Verily, Allah forgives not that partners should be set up with Him in worship, but He forgives except that (anything else) to whom He pleases, and whoever sets up partners with Allah in worship, he has indeed invented a tremendous sin.”(V. 4:48).