Interestingly, the one [mortal sin] that modernity focuses all its energy on -- lust -- has typically been regarded as the least of the seven deadlies (though that's like saying, "Mercury poisoning doesn't kill you as quick as a bullet to the brain").Juxtapose this with Screwtape's advice to the tempter Wormwood:
Indeed the safest road to Hell is the gradual one-the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts.
Of course, Screwtape's advice works equally well (even better?) with more innocuous sins like neglecting your elderly neighbor and bad-mouthing your annoying co-worker, but if Satan had a "pet" mortal sin, lust sure seems to fit the bill.
Other fascinating thoughts at the article previously referenced.