Huge, huge vouch for FactionsKore, its an extremely high quality plugin, full of amazing factions features, I personally own FactionsKore and have used it in many releases, its easy to work w/ and over at Kore Development they're always willing to give you the support you need until your issues or questions are resolved. FactionsKore comes w/ regular updates by an amazing dev. I'd highly recommend, it's a great value product at a reasonable price.
Massive vouch for FactionsKore, it's an amazing project, developed by amazing people, I would highly recommend it. Best part is, everyone who works with/for Kore Development is friendly, knowledgeable and fast at responding.
Kore solves a lot of the problems that modern servers face - unoptimized, janky plugins. Many servers with hundreds of players online simultaneously use this plugin. The amount of features this implements all in one plugin compared to using tens of other plugins is insane. The price for all the features compared to separately sold plugins, has a lot of value.
Vouch for FKore, have used it on servers myself and have seen it in use. Any issues are fixed extremely quickly although there are almost no issues in general as it is so well made. The support team is by far the best I have seen for a development team and the plugin/s themselves are absolutely amazing, perform well on large scale networks and have seemingly endless configuration.