All sins are offenses against God, as well as faults against reason, truth, and right conscience. Sin is a deliberate thought, word, deed, or omission contrary to the eternal law of God.
There are a great many kinds of sins. Scripture provides several lists of them. The Letter to the Galatians contrasts the works of the flesh with the fruit of the Spirit: "Now the works of the flesh are plain: fornication, impurity, licentiousness, idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, factions, envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the Kingdom of God."
Sins can be distinguished according to their objects, as can every human act; or according to the virtues they oppose, by excess or defect; or according to the commandments they violate. They can also be classed according to whether they concern God alone, neighbor, or oneself; they can be divided into spiritual and carnal sins, or again as sins in thought, word, deed, or omission. The root of sin is in the heart of man, in his free will, according to the teaching of the Lord: "For out of the heart come evil thoughts, murder, adultery, fornication, theft, false witness, slander. These are what defile a man." But in the heart also resides charity, the source of the good and pure works, which sin wounds.
Sins are rightly evaluated according to their gravity. The Bible shows that there are sins that lead to death for a Christian, and those that do not: 1 John 5:16-17:
"If anyone sees his brother sinning, if the sin is not deadly, he should pray to God and he will give him life. This is only for those whose sin is not deadly. There is such a thing as deadly sin, about which I do not say that you should pray. All wrongdoing is sin, but there is sin that is not deadly."
Sins which lead to death are called
mortal sins - these destroy charity in the heart of man by a grave violation of God's law; they turn man away from God, who is his ultimate end and his beatitude, by preferring an inferior good to him.
Venial sin allows charity to subsist, even though it offends and wounds it.
So yes, some sins are worse than others but they are all bad. Christ suffered for
all of our sins... and why would someone who loves him intentionally add to his suffering with the thought that, after all, it's not such a big sin?