How does one atone for backbiting, especially when most of the people are forgotten or have passed away? And is it possible to erase past sins and come before God with a clean slate after committing transgressions and shaking the Throne of the Most Merciful?

The door of repentance, by the grace of Allah Almighty, is open to every human being as long as the sun has not risen from the West or death is not witnessed. Allah Almighty loves forgiveness and forgives those who repent to Him and seek His forgiveness. Allah Almighty has promised that He will transform the evil deeds of those who commit major sins into good deeds if they repent, believe, and do righteous deeds. The repentant person must regret their sins, abandon them, resolve not to return to them, restore injustices to their rightful owners, strive to strengthen their faith, remain steadfast in obedience to Allah, and follow up evil deeds with expiating good deeds.