God is infinite. Therefore, any transgression against Him is of infinite evil. Let me illustrate it this way:
If I slap a mosquito no one bats an eye. If I slap a dog a few people might be upset with me. If I slap a child I will most likely be in trouble. If I slap a police office I'll probably get arrested. If I slap the president I may even be tried for treason!
The action is the same. But what's the difference? The person I have committed the action against. So, God is an infinite being, therefore any sin against Him is of infinite evil.
How can I pay an infinite debt against God? I never can. This is why hell is eternal.
Yet, Christ bore our sins in His body on the tree (1 Peter 2:24). The question must be asked: How could Christ pay for the infinite debt owed? Not just for my sin either! But for all the sins of all those who would ever look to Him in faith!
I submit to you that this is an impossibility if Christ is merely a good man. If Jesus is anything less than the infinite God in the flesh, He cannot bear the full weight and penalty for my sin.
But be of good cheer! Jesus is God! The 2nd person of the Trinity. He and the Father shared glory before the foundations of the world (John 17:5). And He will receive glory for all eternity (Revelation 5:9-13).
Any person who denies the Trinity denies the atonement. If one says Jesus is less than God then His sacrifice cannot be enough to actually pay the full price for my sin. If one is a modalist then it is impossible for the Father to impute my sin to the Son so that He can pay for my sin (2 Cor. 5:21).
The Father is God. The Son is God. The Holy Spirit is God (Acts 5:3-4). Each is fully divine. Yet, God is not 'chopped' up. Trinity means 'Tri-Unity'. He is ONE God who eternally exists in Three distinct Persons. This is not a contradiction, but it is a mystery! It is no trifle thing to deny God's own revelation of Himself as God in three persons, blessed Trinity.