Strongest pre-majin form would be Post-Timeskip Dark Schneider who can fight on par with Seraphs. Giving him roughly 7000x FTL speed, planet-level spells, and sun-level durability for tanking a supernova-level ultimate attack from Michael while headless.
Meaning he solos everyone at the same time effortlessly.
Pre-Timeskip D.S. would stop at Madara and at least one of the Kings.
You should have PM a mod. We're not here 24/7 and check every thread. You have to proactive. I just noticed your request 2 weeks from your post. I'll fix your OP even though the image glitch has been taken care of last Thursday.