Every movie now has some sort of green screen or blue screen effect, but what happens when it's done horribly wrong. It's not believable at best and can ruin a movie at worst. The Star Wars prequels come to mind for overuse of CG effects and usage of green/blue screens. The action and scenery never felt real. The immersion was lost in much of these movies as a result.
While there are plenty of great examples of what not to do, Youtube Channel CBR shows 10 of the worst green screen fails. Watch the video below: