2kewl4u said:
Despite the character development of Griffith and Gattsu being >>>>> Zoro and Luffy's.

2
The Eclipse still stands as the best betrayal in anime/manga, or at least contending with a certain character betrayal in Season 4 of Legend of the Galactic Heroes that I won't spoil for the masses that have yet to see it (shameless plug advertising people to go watch the series, I know), mainly since most other character betrayals tend to be executed quite poorly. The question is, would Zoro's betrayal at least be third place? Whilst I'd say the execution of it would be far more important than the premise to avoid it becoming Sasuke/Uryu tier

, I'd say there are a few I can't see it topping, mainly several of the character decisions in Sangokushi or the reveal of John Silver in Takarajima due to both series' betrayals being logical yet not obvious if one wasn't already well read in the source material. Considering the former is based on historical events and the latter an animation of a classic novel, it is questionable as to whether or not they were included.
Getting back to the point, Zoro betraying Luffy would be one of the most impactful betrayals for a series in anime/manga, but I can't see a scenario where it could be anything but illogical.