"Supergirl" actor Tyler Hoechlin's Man of Steel act didn't charm his landlord ... he says the guy screwed him out of $10k when he moved out of his apartment.
Hoechlin and his roomie, Ryan Guzman -- the hot dude from J Lo's "The Boy Next Door" -- are suing their landlord for overcharging them for what they call ... "normal wear and tear" on their crib.
In legal docs, they say the landlord deducted $9,689 from their security deposit to cover paint and other common move-out expenses. They insist there was nothing out of the ordinary done to the place to warrant that tab. They're suing to get their money back.
A rep for the property management company stands by the charges.