The wrath that Paul speaks of in Galatians 5:20 is different from the wrath of God that is mentioned frequently throughout the Bible. There are two Greek words that are used for wrath and they have different connotations. In this list, Paul used the term "thumos". Thumos has two meanings.
The first meaning for this term speaks of a person that quickly loses their temper and has outbursts of anger. People that walk in this work of the flesh are often mentally and/or physically abusive. The second meaning for thumos speaks of fierceness, and in many places, is tied to the wrath of God. It is an intense outpouring of anger that speaks of revenge.
Vengeance is something that we are to leave to God. Deuteronomy 32:35 says "to Me belongeth vengeance and recompence...". God wants us to show kindness to those that wish us harm. King Solomon said in Proverbs 25:21-22 that "if thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink: For thou shalt heap coals of fire upon his head, and the Lord shall reward thee". "Heap coals of fire upon his head" was a Jewish idiom similar to our phrase "kill them with kindness". The Apostle Paul wrote "recompense to no man evil for evil. Provide things honest in the sight of all men. If it be possible, as much as lieth in you, live peaceably with all men. Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord" (Rom. 12:17-19). In both Testaments, God said that people are to repay wrongdoing with love. God is rich in mercy (Eph. 2:4) and wants us to live the same way.
As stated in the first paragraph, there are two Greek words for wrath. The second term is "orge" which implies a prolonged waiting period before revenge. God allowed 430 years to pass before passing judgment on the land of Canaan (see Idolatry lesson for more information) because He is patient (2 Peter 3:9).
"...the fierceness and wrath of Almighty God." - Revelation 19:15
"...the thumos and orge of Almighty God." - Revelation 19:15
A modern way of saying this verse would be "the great intensity of Almighty God's patient revenge". God's patience with mankind is best summed up in 2 Peter verses 8-9:
"But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day. The Lord is not slack concerning His promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance."
Wrath, as listed in Galatians 5:20, is the exact opposite of God's nature.
Next work of the flesh: strife