Unbelievers often think they will be able to argue their case on judgment day. If not just because they believe they've got nothing to answer for, many of them actually think they're perfectly capable of accusing God of some wrongdoing on His part.
But this misguided belief is fueled by a lack of understanding of exactly how morality works. Unbelievers don't think of God as God, but as just another man. His moral views are, at best, equal to theirs, and more than likely actually inferior.
However, as previously pointed out, God has the advantage of being God. That is, nothing is above Him. The universe is His, everything in the universe is His, everyone in the universe is His. For this reason, He gets to make the rules, and judge those who are under them.
One might compare this to us and our creations. Imagine if you were reading this post, but your phone or computer suddenly decided it didn't want you to. "No, I want to play Minecraft instead!" When our creations do not do as we intend for them to do, we usually get quite cross. We either correct the problem, or we discard the offending item and replace it.
As we are God's creations, does God not have the same authority over us? Of course! How can the Creator of everything have less authority over His creations than we have over ours? It would be like saying that selfie you posted on Instagram recently has more of a right to dictate your social media habits than you do.
That reason alone is a trump card God can play any time He likes. You can't answer God one time out of a thousand simply because He is God. But God doesn't typically just leave it at that. He gives reason. Specifically, God has given us a set of laws specifically designed for the purpose of showing us that we are not obedient creations. We do things we were not designed to do, and we don't do things we were designed to do.
This disarms a second defence. "I'm a good person", we like to say. But because we have the law, we see that we are very much not good people. Even the best examples humanity has to offer cannot claim to have never done anything wrong. Indeed, we do it on a daily basis. Not even faithful Christians can stand up and say "I am not a sinner", because we all are. Even going through the 10 commandments, most of us find that we are not only guilty of some of them, but by Biblical definition, wherein sin starts at the heart level, we are actually guilty of all of them.
Should God desire, He could make human beings just for the purposes of sending us to Hell. He's God, it's not like anyone can stop Him. But God does not desire that. We see from the Scriptures that actually, Hell wasn't even designed for man, it was designed for Satan and his angels (Matthew 25:41). But through our sin, we become rebellious creations worthy to be discarded.
Nevertheless, God does not desire this outcome. He is perfectly willing to repair us rather than discard us. Thus, through the death and resurrection of His Son, we can be saved. This is the one and only way we can answer God, and He will accept that answer. That answer is "my debt has been paid by Jesus Christ".