Alagaesia from Eragon might actually stand a chance assuming it’s like the prime of the dragon riders

Dragon Riders(and to a lesser extent wizards) in that are absolutely busted and since Viltrumites wouldn’t have the specific training to resist magic the Viltrumites would be dropping dead left and right to anything from brain aneurysms to spontaneous explosion. If a Viltrumite actually got their hands on anyone in that verse the rider is basically instantly dead but with magic they’d at least trade and kill each other