a lasting (/deep-rooted/irreconcilable) hatred ? 過去互相懷有～的部落，如今友好相處。The clans who held a deep-rooted hatred for each other in the past live in harmony now.
九世之仇jiǔ shì zhī chóu
比喻積怨非常久遠(yuǎn)的仇恨。the national hatred is very far back but revenge, a lasting hatred