(Homebrew by Christopher Zito on dmsguild. Due to the commercial nature of the homebrew, it will be provided to players if they want to play this subclass.)
Some paladins fight for justice, some fight for vengeance, but some just want to prove a point. The Oath of Spite is specifically for the kinds of paladins who can't let grudges go, who fight dirty and whose words carry venom towards the targets of their spite. Generally petty and often quite abrasive, Paladins who take on this oath are not exactly popular, but many people recognize that they and their methods are sometimes necessary to bring justice to evildoers; the effectiveness of a grudge, combined with a sharp tongue can be quite useful in that regard, even if it isn't quite the searing desire for revenge that something like a Vengeance-Paladin might pursue. Many Baphomet take on this oath in their efforts to spite their creator.
Tenets of the Oath of Spite
-Never Forgive, Never Forget. The past transgressions of one's actions will only grow and cast a greater shadow if just action is not delt accordingly. Break the cycle now before sin grows stronger.
-Repay Insult in Kind Justice. Not all sins are grave offenses to the common man, but to not show one the error of their ways and how it would effect them as it does others is doing a disservice to not only your community or the one accountable. It also brings to light your slothfulness and lack of conviction to the oath.
-No Vengeance is Too Petty. The weight of one's crime may not hold high value to some, but to it's victims it could cause irreversible effects and there for chance to very fate of the world around us. Gather evidence, find logic, and strike all wrongdoings in brutal compensation. Sin will never show restraint when faced with judgement, give it no quarter.
-Be Not Blind to Reason. Wear your conviction with pride, but never let it swallow your mind of reason. If one makes a mistake and misjudges the innocent, repay them tenfold.