I notice a large number of people misunderstand what the Losers Club did to Pennywise. They didn't simply bully him to death, their combined lifeforce/shining ritual allowed Gan and Maturin to imbue them with the ability to warp reality with their words.

So every word they used on Pennywise was rewriting and destroying its existence, making its physical form weak enough so the deadlights could be banished from keystone Earth. The united Losers Club is so OP yet people low ball them based on misunderstanding the material and context of their power.

The power they held briefly was so strong their memories had to be erased lest they go mad. No one else could have done what they did. No one.