Do you, my friend, believe that Jesus Christ died for the sins of all men without exception? Perhaps many who read this will answer, Yes. I then ask you, Why are not all men without exception saved? You will probably respond, because they do not believe in Jesus Christ. I will respond that if Christ died for all their sins, He died for their sin of unbelief, and taketh it away as well Jn 1:29, hence as Saviour from sin, He must save from unbelief Matt 1:21. If Christ died for all ones sins, then they must not die for them, for dying in unbelief is equivalent to dying in all your sins Jn 8:24
24 I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins.
You see that, if you die in unbelief, you die in your sins, which supposedly Christ has already died for and satisfied Gods Eternal justice for. In this instance one makes God unjust for punishing someone's sins twice, in Christ their Surety and then in themselves, that's unjust to Christ the Saviour, who suffered and died and the sinner He suffered and died for. However we know God is a Just God and Saviour Isa 45:21
Tell ye, and bring them near; yea, let them take counsel together: who hath declared this from ancient time? who hath told it from that time? have not I the Lord? and there is no God else beside me; a just God and a Saviour; there is none beside me.