Evil done deliberately provokes a severer judgment.  This is worse than committing sin by precipitancy where sin is the more easily washed away.  Those who sin deliberately easily fall also into despair.  "I will visit upon you for the evil of your doings.".  

There is a difference between the sin and evil purpose.  Sins in deed are often due to infirmity or negligence; but, in evil purpose, it is always due to a malicious intent.  

"And he sat not in the seat of pestilence."  To sit in the chair of pestilence is to commit evil deeds with deliberation; it is to discern what is evil by the use of reason and yet commit it deliberately.  He sits in the chair of perverse counsel.  He takes pleasure at accomplishing evil after deliberation.  Sins that are deliberately sought out are the most serious sins.  Such people become the princes of evildoers.  

St. Gregory the Great: Pastoral Care, Chapter 32, Part III

(08-21-10)