What does the Bible say about revenge? What does the Bible say about suing people in court who may owe you money? Would it matter on how much it was? Would it matter if it was a significant other or a friend?
If it was a matter of revenge, then God says, "Repay no one evil for evil. Have regard for good things in the sight of all men. If it is possible, as much as depends on you, live peaceably with all men. Beloved, do not avenge yourselves, but rather give place to wrath; for it is written, "Vengeance is Mine, I will repay," says the Lord" (Romans 12:17-19). But lawsuits are rarely about revenge. It is about the fact that someone incurred a debt and then is not making payments as promised.
Christians should be able to settle disputes among themselves without having to resort to secular courts. "I say this to your shame. Is it so, that there is not a wise man among you, not even one, who will be able to judge between his brethren? But brother goes to law against brother, and that before unbelievers!" (I Corinthians 6:5-6). But not everyone who claims to be a Christian behaves as one.
Suits over debts between husband and wife should be technically impossible since both should be owning everything in common between them.