Oath of the Watchers should start with a broken oath. They failed Vigilance.

I think Vengeance should be in, but it should let the player select their "sworn enemy/enemies" since the game has no alignment to define their "greater evil". That would allow for a more elastic paladin.
Conquest for evil pally who don't want to be a "good pally who fell to darkness" and take Oathbreaker. They should break oath when they spare enemies and use persuasion when there is intimidate option.