It is often said that Saint John Vianney was easier with penitents sins of the flesh than sins of malice. To be sure, a mortal sin is a mortal sin, but the Saint stands on the shoulders of a long theological tradition. Saint Thomas Aquinas teaches the following in his magisterial De Malo:
"Homicidium enim dicitur maius peccatum quam adulterium, non quia magis corrumpat bonum naturale animae, sed quia magis removet bonitatem ipsius actus: plus autem contrariantur caritatis bono."  De malo, q. 1 a. 1 ad 13
(For homicide is said to be a greater sin than adultery, not because it more greatly corrupts the natural good of the soul, but because it more greatly removes the good of the act itself.)
Saint Thomas Aquinas, pray for us.