Here's a guy targeting his roommate[0]. Previous discussion[1].

[0] https://ghostinfluence.com/the-ultimate-retaliation-pranking...

[1] https://news.ycombinator.com/item?id=8330931

By making a Custom Audience and then selectively uploading? I think you have to agree to not do this.

The audience size tricks like uploading an audience, then adding one to it and reuploading won’t work. There’s a cardinality fudging thing.