"It depends" is the right answer. It depends on the denomination you belong to. It depends on where in the bible you are reading. It depends on whether or not you read the bible. It depends how well you can "translate" and rationalize absurdities. It depends on which of many contradictory verses you want to base it on. It depends on whether or not you think the bible needs to be taken in the context of its time. It depends on whether or not God has given you a personal revelation that lets you ignore certain bits in order to work for the greater good (looking at you, Eric Rudolph). It depends on whether or not you think you can just ask for forgiveness later.
So much for an absolute moral position, right?
It is a fascinating concept though, and it is one way in which "honest" Christians set themselves up for abuse. In the churches that I went to it was almost as if the worse the sins a person had committed and repented of (and by sin I mean crime, and serious ones), the better Christian they were. The more freely they confessed their really odious past to us, the more grateful the church seemed to be to have their testimony and their company. Now I do think that a lot of them simply made their sins up to gain credibility, but I assume some of them really did what they say they did. The pragmatic side of this is that the church gives a high status to people who have committed serious crimes, and this really shows, both statistically and anecdotally. The second highest indicator of child molestation in a family, after substance abuse, is traditional or fundamental religiosity. It really fascinates me how Christianity can simultaneously guilt trip some people into feeling like scum because they read Playboy, while giving acceptance and trust to a child molester. Simply telling people that you did something bad doesn't make you a better person.
The general position in the churches that I went to was that all sins were equal in that they equally separated you from Christ, and thus every sin damned you to hell in an equal manner.
A Methodist pastor told me when I was little that the worst sin was this:
Mark 3:29 - But whoever blasphemes against the Holy Spirit will never be forgiven; he is guilty of an eternal sin.
n. pl. blas·phe·mies
a. A contemptuous or profane act, utterance, or writing concerning God or a sacred entity.
b. The act of claiming for oneself the attributes and rights of God.
2. An irreverent or impious act, attitude, or utterance in regard to something considered inviolable or sacrosanct.
Therefore, I deny the Holy Spirit, I am the Holy Spirit and take on all the aspects of Holy Spiritness, and the Holy Spirit is a poo poo head.
Now I'm both smelly and bound for hell. Dearie me.