Need a larger image, and an up-close shot

Poison it. Poison it now.

Probably a holly. It's thoughtless and unfortunate when neighbors plant things that grow into someone else's yard, which is what it looks like happened here from what I can see in this tiny picture. Maybe it just sprung up from seed. You're, of course, entitled to chop off whatever parts are on your side of the fence, but probably not a chore you ever wanted to have. Maybe the neighbors would move it if they did put it there and are made aware of the issue.