But the worse sin of all, of course, is unbelief.
It´s the third sin to appear in the Bible, in the times of Noah (skipping over a few minor narrations). The people in Noah´s days were too busy with their lives. Noah spent 100 years building an ark and warning that a world-wide flood was coming.
But it had never rained on Earth before (crops were watered by a constant mist/fog), so talk of “rain” seemed ridiculous to them. Why didn’t they enter the Ark to escape God’s wrath? There was plenty of room. Because of unbelief.
Jesus describes in the unpardonable sin. I believe this is nothing more than not believing Jesus. The Pharisees rejected Jesus, despised the conviction of the Holy Spirit, and that is what Jesus called unpardonable.
If pride is the sneakiest sin and jealousy the scariest, the unbelief is the most dangerous. The reason? If you believe, you can be forgiven of all sins. If you don’t believe, you don’t even ask God for forgiveness.