Hm...so Radke is going to play that kind of, huh? Let's put this to our advantage!
Okay Lumber, this may be strange, but I want you to use Payback first! Since Counter always goes last, this should be half as powerful, and should deal just around 7 damage. You won't take much damage from Counter this way, and it'll be enough to KO it after another Drain Punch, forcing it to use Return.
Then, I want you to combine your Mach Punch and your Drain Punch to make your Drain Punch go first! The speed you gain off of the Mach Punch should enable you to go first before Radke can Return you, and the power of Drain Punch should nab you the KO before it hits you!
So:
Payback -> Mach Punch + Drain Punch