Only perfection qualifies for Heaven and that causes a big problem. For God to be just, he cannot sweep sin under the carpet. Let's imagine that we were travelling 50km over the speed limit. I was in the lead and you were following me in your car. We whiz past a radar trap and the police let me go and stop you.
Justice demands that the law be applied fairly and evenly.
An infraction is an infraction. For God to be just, all sin must be dealt with and a penalty accessed. The Bible calls that redemption. Adam and Eve sinned and passed their sin nature on to all mankind. Death came by one person.