Now therefore go, and I will be with thy mouth, and teach thee what thou shalt say. (Ex 4:12)
What is revenge??? Defined, it is "To inflict punishment in return for (injury or insult); to seek or take vengeance for (oneself or another person); avenge." The thesaurus gives vengeance and avenge as "synonyms" for revenge.
Throughout the Bible we are told of God's wrath, how time and time again he has avenged his people! We don't have to read any further than Genesis when Cain killed Abel - God's vengeance towards him for killing Abel (and sevenfold to anyone who killed Cain) caused him to be cursed and "when thou tillest the ground, it shall not henceforth yield unto thee her strength; a fugitive and a vagabond shalt thou be in the earth." (Gen 4:12)
Then a while later in Genesis we have Noah and his task; we also have the tale of Sodom and Gomorrah. If we stroll over to Exodus, we find a whole boatload of opportunities offered to the Pharaoh to release from bondage the Israelites. How many times was he asked??? How many plagues visited him??? What was the ultimate sacrifice??? And did they learn their lesson??? I now direct your attention to the parting of the Red Sea (and subsequent demise of the Egyptians who thought it would be a good idea to pursue the Israelites - aka God's People!!!) And the vengeance continues!
God does not deal in "karma". He deals in mercy and grace for those who follow his path and obey his laws. He offers eternal life, free of charge (paid for in blood - for us - by Jesus), if we accept that gift of grace through faith. He deals in vengeance when his authority is opposed and he can do that - he is GOD - he makes the rules and even tells us the consequences if we don't follow Jesus (and I think it's a safe bet that the fiery lake that John tells us about in Revelation is a tad bit hotter than the Jersey Shore in August).
Don't ever presume to tell anyone what God does or doesn't do if you haven't read his book. It's called "The Bible" and it's written with you in mind. Check it out, it's a rather good read, if I do say so myself...but that's just my opinion. You may find that the targets of his vengeance are those who blatantly disregard his laws (as in Leviticus 20). If you aren't convinced after reading this post that God does, in fact, take revenge for his people, continue on the path you are on and you will experience his wrath, first hand. As in Nehum 1:2, "God [is] jealous, and the LORD revengeth; the LORD revengeth, and [is] furious; the LORD will take vengeance on his adversaries, and he reserveth [wrath] for his enemies."