Is insulting the Lord and one's parents among the greatest forms of disbelief and the greatest sins, and is it more severe than the disbelief of idol worship?

Blaspheming God and religion is considered one of the most severe forms of disbelief (kufr). Ibn Taymiyyah stated in "As-Sarim al-Maslul" that whoever among Muslims blasphemes Allah Almighty must be killed by consensus, because he is an apostate disbeliever and worse than a disbeliever. People are in agreement about killing him, but they differ regarding the acceptance of his repentance.