question #2 Sahih al-Bukhari 6871, Book 87, Hadith 10 : Why is associating partners with Allah considered a major sin in Islam?

The Prophet (ﷺ) said, “The biggest of Al-Ka`ba’ir (the great sins) are (1) to join others as partners in
worship with Allah, (2) to murder a human being, (3) to be undutiful to one’s parents (4) and to make
a false statement,” or said, “to give a false witness.”