The best there is, but not free. https://www.vbulletin.com/ (https://www.vbulletin.com/)
Vbulletin installing is not for the faint of heart. You should have some experience with databases and php, or have someone else install. http://www.bigkahunahosting.com/hosting-services/ (http://www.bigkahunahosting.com/hosting-services/)
Vbulletin will take one database
an example of a Vbulletin from on BHK is https://www.joebidennotmypresident.com/forum/
BHK excels at installation and upgrading of Vbulletin, because we don't throttle resources like the discount servers do. If you've ever tried to install vbulletin on Go Daddy, you've most likely also contemplated suicide too while installing. We let our accounts utilize all available server resources to get the job done quickly.
I have a Vbulletin Connect 5 perpetual license that I'm not using and interested in selling a transfer. I can also install for you with the latest update and handle as much configuration as you want. Submit a support ticket if you're interested.