When people die naked in their sin, without the protective armor of God's grace given to all with faith in Christ, hell, separation from God, is their destination. Jesus warned of this when He told Nicodemus, "Those who believe in [Jesus] are not condemned; but those who do not believe in Him are condemned already, because they have not believed in the name of the only Son of God" (John 3:18).
Jesus made His atoning sacrifice complete by sharing not only in death, but also in the experience of hell itself. 1 Peter 3:18-20 says:
For Christ also suffered for sins once for all, the righteous for the unrighteous, in order to bring you to God. He was put to death in the flesh, but made alive in the spirit, 19in which also he went and made a proclamation to the spirits in prison, 20who in former times did not obey, when God waited patiently in the days of Noah, during the building of the ark, in which a few, that is, eight persons, were saved through water.(Peter goes on, by the way, to speak of baptism as the means by which the old self is drowned and God's Holy Spirit brings new life in Christ.)
We remember Maundy Thursday as the day on which Jesus, with His face set toward dying for us, instituted the Sacrament of His Body and Blood (Holy Communion, The Lord's Supper, The Eucharist) and gave a new command to His Church: that believers love one another as Christ loved us, sacrificially.
We remember Good Friday as the day on which sinless God-enfleshed died in our places on the cross, so that all who believe in Him will find their sins covered by His life-giving blood and grace, His undeserved favor.
We remember Easter Sunday, of course, as the day when Jesus rose from the dead, claiming eternal life with God for all who believe in (that is, entrust their lives to) Jesus Christ.
We should also remember Holy Saturday, the day on which Jesus bore the full punishment our sins merit, descending into hell, but at the same time, proclaiming that God's plan had been fulfilled; the perfect sacrifice had been offered; the powers of the devil, evil, and hell had been crushed for all eternity. The devil, evil, and hell still wreak havoc in this world. They will until the day when Christ returns to fully establish His kingdom. But they are in their death throes. Christ has conquered!