If the person has no mortal sins on their soul because they repented, confessed and were absolved, then their past prior to their absolution ceases to matter.
If the person has committed additional unconfessed grave sins since their last confession, they need to confess again, and as soon as possible because they might die at any time. They should also immediately make an act of perfect contrition to God, which would help them in the event that they died before the priest could arrive.
In your scenario you talk about somebody who “does not have any mortal sins on their soul” but somehow managed to “die without final repentance”. This doesn’t make any sense. If a person doesn’t have mortal sin on their soul then there’s nothing to repent from except ordinary venial sins, and unrepented venial sins don’t send a person to Hell.
In short, a person who dies with no mortal sin on their soul is going to go to either Heaven directly, or to Purgatory for a while and then to Heaven if God decides the person needs more purification before they enter Heaven.
A person who dies with unrepented and thus unabsolved mortal sin on their soul is likely to go to Hell.
A person who dies having repented their mortal sins and planned to confess them, but having not actually gotten to confession before death through no fault of their own (let’s say the person was hit by a bus on the way to go confess, or the priest was late arriving at the hospital and the person had already died by the time he arrived to hear their confession), is likely to go to Purgatory for some time and then on to Heaven.
These are the only possible scenarios.
