What if a person dies while being an outcast, leaving no trace or deed by which people remember them?

Fear of death is of two types: a healthy one that motivates obedience, and a pathological one that causes depression and laziness in worship. The Muslim's duty is to make Allah's pleasure their goal, by fulfilling His commands and refraining from His prohibitions. The important thing is to depart from this world with one's Lord being pleased with them.