As with any large ensemble cast, the important thing in It Chapter 2 is balance. That goes particularly to this film because of its admirable attempt to mesh two separate timelines and two different "realities" in each together to create one cohesive, coherent narrative.
It should probably go without saying that there are some compromises in that balance - with some characters being left behind almost entirely in fact - but with a cast this good and performances in the first film so good, it was still always going to be an entertaining experience. What counts now, though, is working out who walked away as the best characters. Remarkably, it wasn't Pennywise.
For this, let's go with characters who influence the plot in some way. There are obviously characters created solely as projections by It, like Eddie's mom and Georgie (credited as Dead Georgie, which is nice) and Mr Keene the pharmacist and his daughter Gretta (both the young and older version) but they're pretty minimal and don't really need to be in the ranking. That said there are other supporting figures who DO deserve their own mention...
15. The Shopkeeper - Stephen King
The film is actually pretty nicely punctuated by references for Stephen King fans (and horror fans) - including the "Here's Johnny!" thrown in there - but the most on-the-nose is definitely the appearance by the great man himself.
He appears as an antiques dealer who Bill encounters in a case of the most meta reference ever (Bill is, after all, a thinly-veiled cipher for King too), criticises him for his lack of finesse in ending stories (insert Spider-man pointing at Spider-Man gif in your own head here) and then sells him his own bike.
It's just fan-bait and a little silly, even if it's nice to see him included, and there's an unfortunate feeling that King is so strange looking that he's going to end up being a monster. And then he's just sort of not.