What Are The Worst Major Sins?

The Prophet (pbuh) said,
"Shall I tell you of the worst major sins? Worshipping others with Allah, showing disrespect to parents, giving a false statement, and testifying to the truth of a falsehood. " And he kept repeating it until we were telling ourselves (out of sympathy for him because of the strain of repeating it), "If only he would be silent.” (Bukhari, Muslim and Tirmidhi)