Will the killer who was executed in this world be exempted from Allah's punishment and accountability, or will Allah hold him accountable without punishment based on his having received his worldly recompense?

Whoever has the death penalty carried out upon him in this world, his sin is atoned for – according to the preponderant opinion – and he will not be punished for it in the Hereafter; because Allah the Almighty is too noble to punish His servant for a sin twice. This applies if the sin is between the servant and his Lord. However, if it relates to a human right, such as murder, then if the killer surrenders himself to the victim's guardians and is executed or pardoned, his accountability is cleared. Ibn al-Qayyim holds that the killer's right is related to three rights: the right of Allah, the right of the murdered, and the right of the guardian. These rights are dropped by repentance, execution, reconciliation, or pardon, and the right of the murdered remains, for which Allah will compensate him on the Day of Judgment. The conclusion is that whoever repents from the crime of murder and has the punishment carried out upon him, it is hoped that he will not be punished in the Hereafter.