You see, mankind is fallen. Sin is a very part of our DNA. The darkness is man's norm. As Saint Paul rightly said that the wages for your sin is Eternal Death. There is no other way. May cannot pay for their own sins because our sins are countless.
However, God takes no pleasure in the eternal death of anyone. This Death grieves Him. Sin grieves Him. If He wouldn't take sin into account and punish it, He would oppose His very nature; He would break His own righteousness. Hence, He punishes Sin.
God wanted to make a way for everyone once and for all. He wanted us to be reconciled to Him forever. But GOD has shown the path of Sinners to go to Heaven and the Righteous to end up in Hell.