A single major sin does not erase all good deeds, but it may erase an equivalent amount of them, according to the opinion of most of Ahl As-Sunnah. Nothing erases all good deeds except disbelief, just as nothing erases all bad deeds except a sincere repentance.

Determining whether someone is a kafir or a fasiq is not up to us, rather it is up to Allah and His Messenger (peace and blessings be upon him). No one may be judged to be a kafir or fasiq except the one whom the Quran and Sunnah indicate is a kafir or fasiq.

Ahl As-Sunnah wal-Jama`ah believe that good deeds are not accepted if they are accompanied by disbelief, and that nothing cancels out all good deeds except disbelief. However, some bad deeds erase some good deeds but they may be restored if one repents.