The sin of envy is often associated with covetousness. Although they are similar and can be intertwined (just as adultery and fornication can be), they are different. I will go into more detail on envyings in a moment, but the easiest way that helps me differentiate the two is like this:
When a person covets, they want to own another person's possession (Ex. 20:17, Deut. 5:21).
When a person envies, they want what the other person has because they believe that they are more deserving i.e. they hold a grudge.
The Greek term used in Galatians 5:21 is "fqonoj" (pronounced thon-os). This term that is translated as "envyings" has a stronger meaning than what we often think of when it comes to envy. To fully understand what Paul was saying it would be easiest if I combine familiar English terms.
To commit fqonoj is to want what another person has because they do not deserve it - you do; and because this person does not deserve the object of your desire, that person should have it ripped away and given to you. In essence, it is the combination of jealousy, covetousness, and spite.
The Bible gives a plethora of examples of how evil this sin is. Joseph's brothers faked his death and sold him into slavery (Gen. 37:18-35). Our Lord was delivered over to death by His own people out of envy (Matt. 27:18). The Jews sought to sabotage the ministry of Paul and have him killed because of envy (Acts 13:45, 17:4-6). I hope that you noticed that the goal of envy was the death of the innocent.
Is it any wonder why King Solomon asked "who is able to stand before envy?" and said that it is worse than anger and wrath in Proverbs 27:4?
As Christians, members of the Kingdom of God, to wish pain or death upon our brethren or the unsaved because we want what they have is disgusting and grieves the Holy Spirit!
Next work of the flesh: murders