Can you force a villager off your island?

Well, I mean you could make several complaints in a row to Isabel to speed the process up, or use fences to entirely isolate them until they want to move away. Otherwise, I'm not sure of any other way. Hope this helps! :)

I actually know of another way! Time travel. If you don't know what that is, all you gotta do is go to the settings of the game and change the time/date. Make sure to change it back though when you're done.