7. Henry Bowers - Teach Grant/Nicholas Hamilton
Henry Bowers deserved way more screentime in It Chapter 2. When he's broken out of his psychiatric hospital home thanks to It's influence, we get to see the beginnings of a great little dynamic on screen, between him and his dead buddy Patrick Hockstetter, who becomes his chauffeur. Now, putting aside how little sense that makes, it's a great moment and it sets up Bowers being a great secondary antagonist.
Unfortunately, even with so much run-time to play with, Bowers ends up being completely under-played. There's no explanation of his dynamic with It (which is odd, because some elements of the plot are PAINSTAKINGLY explained) and instead you get no real handle on whether he's really being guided by Hockstetter or if it's a murderer's delusion.
And because he's underused so much and ends up adding precisely nothing to the plot, you have to feel like he should have been left out.