Westminster Shorter Catechism #83

Q: Are all transgressions of the law equally heinous? 
A: Some sins in themselves, and by reason of several aggravations, are more heinous in the sight of God than others. 
1 John 5:16-17 If anyone sees his brother committing a sin not leading to death, he shall ask, and God will give him life-to those who commit sins that do not lead to death. There is sin that leads to death; I do not say that one should pray for that. All wrongdoing is sin, but there is sin that does not lead to death. 

It's important to remember, as we look at this week's question, that all sin is worthy of God's anger, wrath, and judgment. All sin is rebellion against God and is a severe offense to his holiness. The point of this question is not to deny this reality. Rather, it is to show that while all sins are equally offensive to God and carry with it the same ultimate punishment (death) apart from God's grace and mercy, God does view some sins as being more "evil" than others. 

What sins are more heinous than others? First, sins that are deliberately against God. Now it is true, all sins are really an offense and sin against God, but some are intentionally so. 1 Samuel 2 gives us the account of Eli's sons, who were deliberately offensive to God. They deliberately defiled sacrifices, and 1 Sam. 2:17 states, "Thu the sin of the young men was very great in the sign of the LORD, for the men treated the offering of the LORD with contempt."

Secondly, sins may be considered more "evil" in the sight of God based upon the harm they cause to others. For example, murdering someone does more harm to them than harming their marriage. Harming their marriage does more harm than stealing physical possessions. Stealing does more harm than coveting. 

Thirdly, the position a person holds adds weight to the sin. James 3:1, for example, states that those who are teachers will be held to a higher standard, "judged with greater strictness" than those who are not teachers. 

Fourthly, and perhaps most difficult for us to swallow, the sins of God's people are eviler in the eyes of the Lord than the sins of those outside of the family of God. When we as Christians sin, we do it as people who know the Lord. We know his commands. We are in personal relationship to him. It is a greater hypocrisy when we as the people of God sin. We, unlike the non-believer, have the Holy Spirit dwelling in us. We have help in our fight against sin, and when we give into temptation and sin, we quench the Spirit and we bring shame to the name of Jesus Christ. It's as Paul says in Romans 2:23-24, "You who boast in the law dishonor God by breaking the law. For as it is written, 'The name of God is blasphemed among the Gentiles because of you.'"

For this reason, we as Christians should grief over our sins more than anyone. We should see our own sins as the most severe. And yet, we also should take comfort and rejoice, because we know that while our sins may be more "evil", while our sins can bring shame to the name of Jesus Christ and quench the Spirit of God, we know that God's grace far exceeds our sinfulness. We know that there is no condemnation for those who are in Christ Jesus(Romans 1:1), and we know that nothing, not even our own sin, can separate us from the love of God in Christ Jesus our Lord (Romans 1:38).