I am having the same problem with the same blue hair guy, nothing I try will get rid of him. I hope the next game update comes out soon along with the fix for this glitch included in it. But thus far I love the game overall (outside of a few issues).
March 2018 - last edited March 2018
Thanks for your reports about this - we will take a look into the stalker Sims (I bet they won't like to be stalked by us)!
In all seriousness, sorry to read you are having an annoying visitor, I can understand having a stranger in the house all the time can be frustrating. One question: none of your Sims have a relationship with the foreign Sim, right? Could you check if they are listed in your Sims' relationship panels?
@MattTheGamer96 Please, avoid duplicating posts, as this can be considered spam, I've merged all your posts into a single answer