Double rinne Madara was knocked on his ass by Gai and these are manga facts.
1st, for convenience Kishimoto made it so Madara would stay of the defensive, Madara could have easily killed Guy.
2nd, Guy is only Raditz level are far as I'm concerned.
He's comparable to Frieza I'd say
Pure fanfic. Madara didn't get the second Rinnegan until after 8th gate, and Naruto and Sasuke fought him for a bit.