Pride (Latin: superbia) is considered, on almost every list, the original and most serious of the seven deadly sins. Out of the seven, it is the most angelical, or demonic. It is also thought to be the source of the other capital sins. Also known as hubris (from ancient Greek ὕβρις), or futility, it is identified as dangerously corrupt selfishness, the putting of one's own desires, urges, wants, and whims before the welfare of other people.
In even more destructive cases, it is irrationally believing that one is essentially and necessarily better, superior, or more important than others, failing to acknowledge the accomplishments of others, and excessive admiration of the personal image or self (especially forgetting one's own lack of divinity, and refusing to acknowledge one's own limits, faults, or wrongs as a human being).
What the weak head with strongest bias rules, Is pride, the never-failing vice of fools.
— Alexander Pope, An Essay on Criticism, line 203.
As pride has been labelled the father of all sins, it has been deemed the devil's most prominent trait. C.S. Lewis writes, in Mere Christianity, that pride is the "anti-God" state, the position in which the ego and the self are directly opposed to God: "Unchastity, anger, greed, drunkenness, and all that, are mere fleabites in comparison: it was through Pride that the devil became the devil: Pride leads to every other vice: it is the complete anti-God state of mind." Pride is understood to sever the spirit from God, as well as His life-and-grace-giving Presence.
One can be prideful for different reasons. Author Ichabod Spencer states that "spiritual pride is the worst kind of pride, if not worst snare of the devil. The heart is particularly deceitful on this one thing." Jonathan Edwards said "remember that pride is the worst viper that is in the heart, the greatest disturber of the soul's peace and sweet communion with Christ; it was the first sin that ever was, and lies lowest in the foundation of Satan's whole building, and is the most difficultly rooted out, and is the most hidden, secret and deceitful of all lusts, and often creeps in, insensibly, into the midst of religion and sometimes under the disguise of humility."
I still think greed is the deadliest, it seems to tie in the most with "money is the root of all evil"