You seem to suggest that the target of the vengeance paladin is ordinary.
Mobsters and Thieves' Guilds are examples you give.
While that obviously isn't against the rules, I don't think it is the assumption/intent. The tenants are about fighting the greater evil. Swearing vengeance against the school bully isn't really what we're talking about here.
It's more about ignoring the thieves' guild in order to concentrate on the archdevils. Yes, the thieves' guild is probably doing some wrong and a devotion paladin would be more likely to try to stop them from stealing from the townsfolk. A vengeance paladin doesn't care about such small grievances.
Yes, we could try to save that village from the gnolls, but if we do that we may allow the archdevils to corrupt the entire realm. That's the sort of thing we're talking about here.
The vengeance is for the greater good, not out of selfishness or the joy of slaughter.