What is the comprehensive explanation of the circumstances and occasions of the hadiths that speak of entering Hellfire because of a cat, or harming neighbors, or suicide, or a person's state changing from doing the deeds of the people of Paradise to doing the deeds of the people of Hellfire, in light of the hadiths that speak of the vastness of Allah's forgiveness and mercy?

The believer must submit to the words of revelation and have good faith in Allah, and he must combine hope with fear. Major sins do not nullify all good deeds, nor do they prevent their acceptance. However, they may nullify a portion of them according to their weight when deeds are weighed. Nothing nullifies all good deeds except disbelief (kufr). What matters is the ending, for deeds are judged by their conclusions. A man may perform deeds that appear to people to be those of the people of Paradise, yet he is among the people of Hell, and vice versa. And endings are inherited from beginnings, and a bad ending may be due to a hidden inner corruption that people are unaware of.