First of all Naruto in his Full blown incarnation of Asura using Kurama to conjure up three heads, near the end of the Manga Naruto also attains 25% of the 8 remaining Bijuu making is multi-elemental Rasenshuriken one of the most destructive Ninjutsu of all time. A jutsu like that could surely...
Madara out of pure desperation gouged out Izunas' eyes and implanted them into himself. I hope that answers your question. Izuna I guess was too shocked to react and had no idea what was actually going on kind of let him.