The Incarnation through the death of Christ makes it possible for God to be "just, and the justifier of him that believeth in Jesus." If God should be merciful without the satisfaction of justice, He would cease to be a God of justice and would thus forfeit His throne of righteousness. In a word, He would cease to be God.
You are not going to be lost when you get to hell. If you are without Christ, you are lost right now. Your trial is already over. You've already been sentenced. You're just waiting for execution morning to roll around.
God in his infinite mercy has devised a way by which justice can be satisfied, and yet mercy can be triumphant. Jesus Christ, the only begotten of the Father, took upon himself the form of man, and offered unto Divine Justice that which was accepted as an equivalent for the punishment due to all his people.
I feel that if God should smite me now, without hope or offer of mercy, to the lowest hell, I should only have what I justly deserve; and I feel that if I be not punished for my sins, or if there be not some plan found by which my sin can be punished in another, I cannot understand how God can be just at all: how shall he be Judge of all the earth, if he suffer offenses to go unpunished?"
When men talk of a little hell, it is because they think they have only a little sin, and believe in a little Saviour; it is all little together. But when you get a great sense of sin, you want a great Saviour, and fell that, if you do not have Him, you will fall into a great destruction, and suffer a great punishment at the hands of the great God.
When God balances the scales morally, it is not some standard outside Himself He looks at and then determines whether this is right or wrong. But rather it's His very nature, it is His very character and nature that is the standard by which He judges.
When justice is divorced from morality, when rights of individuals are separated from right and wrong, the only definition you have left for justice is the right for every individual to do as he pleases. And the end of that road is anarchy and barbarism.