If a person, scripturally married, commits adultery and ends up divorced, can the one who committed the adultery remarry if the one who was innocent dies?
"For the woman who has a husband is bound by the law to her husband as long as he lives. But if the husband dies, she is released from the law of her husband. So then if, while her husband lives, she marries another man, she will be called an adulteress; but if her husband dies, she is free from that law, so that she is no adulteress, though she has married another man" (Romans 7:2-3).
The marriage covenant lasts as long as the husband and wife both live. The death of either one ends the covenant. Therefore, a person who committed adultery is free to remarry after his or her spouse dies.
This loose period of time seems odd to some, but it has precedence. Under the Law of Moses, if a person committed accidental murder, he was restricted to the cities of refuge until the current high priest dies. "So the congregation shall deliver the manslayer from the hand of the avenger of blood, and the congregation shall return him to the city of refuge where he had fled, and he shall remain there until the death of the high priest who was anointed with the holy oil" (Numbers 35:25). The term of his sentence is completely variable. He might be there a few months or many decades.