Sin, by definition, is a violation of God’s law (1 John 3:4). It may be doing what He prohibits or not doing what He requires. It may be in thought, word, or deed. It may even be violating our own consciences in a matter that otherwise would not be wrong (Romans 14:22-23).
Are some sins worse than others? In one way, yes. Those that stem from an openly defiant heart are surely more heinous than those committed in a moment of weakness. There is also a profound difference in the effect various offenses might have on someone else (e.g., profanity vs. murder). The differing penalties for various transgressions under the Law of Moses illustrates that God sees some differences in sins.
However, in another way all sins are the same. Each one indicates a disregard, at least for the moment, for God. Each elevates our will above His. Each has the same effect of making us guilty. That is the point James was making when he wrote, “For whoever keeps the whole law and yet stumbles in one point, he has become guilty of all” (2:10).
Categorizing sins is dangerous. It tends to make us minimize them. (James’s context is the sin of partiality, which some may have viewed as not so bad.) Instead of downplaying them, let’s work on eliminating them.