This fight was quite popular a few years back. Of course Oro lost every time. That's why he gets a few advantages here.

This is Naraku in his first form.

vs.

Orochimaru with:
Manda summoned
Grass Long Sword/Kusanagi Sword already drawn
Unlimited Oral Rebirth
The reanimated First and Second Hokage

Even with all those factors in his favor, not sure if Oro can win.