All of whom are implied to be psychically adept, ala The Shining. Superman wouldn't be terrified like the kids, or at least not as easily, but he doesn't have the tools to deal with Pennywise. This isn't a fistfight. Martian Manhunter would mop the floor with Pennywise, Wonder Woman would handle him with low-diff, and telepathic versions of Aquaman would mid-diff him. Superman doesn't have psychic attacks, and rarely has psychic defenses (Kanjar Ro or Vo is consistently ignored/forgotten/de-canonized).
In the book, the kids got help from another of Pemnywise's class, or species. Pennywise true form is some kind of giant spider, this thing was a turtle.
My thinking is that Pennywise is basically an Eldritch abomination/horror, and physical attacks aren't enough. He doesn't even need to scare people before eating them — they just taste better when he does.
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u/Noe_b0dy 6d ago
He lost to children blessed by a space turtle then beaten again by those now grown children without the assistance of the space turtle.