The damage from Tyranitar's "Power Claw" attack isn't affected by Poke-POWERS, Poke-BODIES, or any other effects on the Defending Pokemon. Would you apply weakness and resistance to its damage?
Yes, weakness or resistance to Tyrantitar's type would be applied where appropriate. These are game rules and not considered effects on the Defending Pokemon.
Source: Unleashed FAQ (2010-05-13), PUI Rules Team (2010-05-13)