A second misunderstanding that this question assumes is that there is no just reason that God would end the physical life part of a human being. This question is also extended into the discussion of whether Hell or any eternal punishment is morally right. The misunderstanding here is that we fail to properly appreciate the gravity of the nature of our sin. The death that God causes in the Bible is generally a result of judgment for sin. This judgement persists into eternal punishment. In this we must recognize the nature of what sin is. Sin is essentially boiled down to one word, which is “rebellion”. Sin is us as human beings saying we want to be free from God. This was the motivation in the garden, that we would “be like” God and therefore have no need of God (Genesis 3:5-7). The second most troubling thing about sin is that it desires to be completely separated from God and everything that He is. The most troubling thing about sin is that ultimately it will get what it wants. The ultimate punishment of sin is that God will withdrawal from the sinner to the extent that they will not understand or feel the presence of God at all. This is what 2nd Thessalonians 1:7-9 says clearly.
…and to grant relief to you who are afflicted as well as to us, when the Lord Jesus is revealed from heaven with his mighty angels 8 in flaming fire, inflicting vengeance on those who do not know God and on those who do not obey the gospel of our Lord Jesus. 9 They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might… -2 Th 1:7–9
There it is speaking of the ultimate judgement of Christ on sin in which They (unrepentant sinners) will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might. The ultimate punishment of sin is that God gives the sinner what He wants and separates Himself from the sinner. The problem is that since life, love, joy, fulfillment, peace, grace, and a myriad of the character traits of God whose beauty we experience imperfectly in life, will be completely absent in Hell. Hell is to exist without the God from whom true life comes. This is a serious thing, and if we are to truly be unrepentant and rebellious, that means that God as the giver and sustainer of life eventually must separate himself from us, and no human life can exist without God. Death and the punishment for sin do not mean God is taking revenge for us disobeying Him. It means that we are saying “God, I don’t want you. Leave me alone.” And God is consenting to do so. It is a serious thing, and yet to the rebel it is their desire not God’s. God is just in the fact that He gives us the invitation to accept Him, and the opportunity to reject Him, but both of these have consequences. To accept God is to experience Him fully, and to reject God is to fail to experience Him at all.