Thank you for your question. The dilemma in this question is caused by the way it is framed as it assumes that punishment is in accordance with specific crimes. One direct answer to this question as it stands is to hypothesize that some crimes would have far enough reaching consequences to deserve eternal punishment. Especially, when those crimes include others and have far-reaching implications into their futures and the people surrounding them.
However, another way to answer the question is to re-frame it and examine life as an opportunity in which people choose how to fashion their own afterlife. In this case, it is not God that enforces an external punishment that would be just or unjust, but rather, the solidification of disbelief in the heart, from which there is no coming back as there is no repentance, manifests as an eternal punishment from which there is no hope of salvation.
May you always be successful.