As we know, there are major sins (Kaba'er) and minor sins (Sagha'er). The major sins are clearly mentioned in both the Qur'an and the Sunnah of the Prophet (PBUH). So, the scale will typically be the order they were mentioned in a verse or a Hadith, and/or the number of Verses/ahadith that major sin was mentioned in (this is my own understanding).
Back to your question in the example you provided:
For example how does eating pork compare to adultery?
Adultery is considered a major sin. There is a specific punishment for those who commit adultery, unlike eating pork, even though both are sins and we should be avoiding them. Also, the amount of verses/Ahadith that talked about Adultery and the punishment for those who commit it can tell you how major it is in the eyes of Allah (SWT).