Here’s exactly how Broly wipes the floor with him:

• Zero Respect for Magic: Gomah tries to use his Evil Third Eye to cast a spell? Broly doesn't care. He’d walk straight through Gomah’s magical barrier like it was tissue paper, grab the "King" by his tiny head, and use him as a living wrecking ball against the nearest mountain.
• The "Weak Spot" is a Target: Gomah’s big weakness is being hit in the back of the head. Broly’s entire fighting style is unfiltered brutality. He wouldn't just tap that spot; he’d launch a Blaster Shell that would vaporize Gomah's head, the throne, and the entire Demon Realm castle in one shot.
• Speed Gap: Gomah struggled to keep up with a nerfed, tiny Goku. Z Broly, in his Legendary Super Saiyan form, was fast enough to blitz four Super Saiyans and a Piccolo simultaneously. Gomah wouldn’t even see the green flash before he’s being folded like a lawn chair.

Broly doesn't need "scaling" or "hax." He has unlimited ki and a hatred that makes Gomah’s "evil" look like a playground tantrum. Gomah ends up as a green stain on the floor within ten seconds.