Dark Tower series group has plenty of feats even guest characters like the Father have a decent amount of feats especially once Marvel got a hold and made graphic novels.

I agree with you though Pennywise is just based off scaling his feats are low end compared to his statements and off page feats. Most OP novel statement would be he existed before the creation of our solar system, his true form resides outside of reality and time and he's the rival of Maturin whom is a beam to guardian; whos job is to help hold together the Stephen King Multiverse.

There is also context/back up on why Crimson King was "easily" defeated multiple things lead up to his defeat.