Hello, can you make an Oathbreaker in this game?

oathbreaker is a 5e d&d archetype. this game is based on pathfinder rules, so no, there is not

Pathfinder DOES have the Antipaladin.
https://www.d20pfsrd.com/classes/alternate-classes/antipaladin/

Not implemented in this game, however.

There's also the Vindictive Bastard, whose name cannot but help make me laugh, and I think somebody is working on it as a class mod.
https://www.d20pfsrd.com/classes/core-classes/paladin/archetypes/paizo-paladin-archetypes/vindictive-bastard-ex-paladin-archetype/

Thank you.