Actually if you start with the original Christian religion, Catholicism, not all sins are equal. There are mortal sins and venial sins. Mortal sins result in eternal damnation while venial sins are absolved by a period of suffering prior to entering into heaven.
I am making no attempt to classify the nature of these sins only pointing out that your blanket statement that the punishment for all sins is equal may not necessarily be true.
It is
...the original Christian religion, Catholicism,...
That is not true, though.