When did you realize the the show had foresworn the Light?

I was quite skeptical about the show from before the start, what with the decision to make wetlands demographics that of modern day Brooklyn, but still, I thought it would be something semi-decent like The Witcher, not the abomination it actually turned out to be, failing not only as an adaptation but by its own standards.

I would say that the precise moment I realized that was the scene at the beginning of Episode 2 where the Whitecloaks burn the Yellow Aes Sedai to death.

At that point, it became clear Rafe couldn't care less about world consistency at the most fundamental and even metaphysical level. We know that any Aes Sedai would have little trouble with a company of Whitecloaks. The only way they'd be able to defeat one is by poisoning or with a lucky bowshot. Capturing one is impossible, short of serving her a very specific sort of tea. But it's not just that one Aes Sedai, but apparently multiple Aes Sedai who were captured and burned by the Whitecloaks.

I did try to brainstorm possibly explanations. Perhaps they'd captured and burned some unfortunate wilder, who was merely pretending to be an Aes Sedai. Perhaps Valda and his buddies had a certain foxhead medallion. Perhaps this show's Whitecloaks had some special anti-One Power weapon, e.g. an Age of Legends machine that produced ter'angreal with a channeling suppressing radius effect. (IMO this might have actually been a cool addition to the books, to make the Whitecloaks a much more powerful faction). But it was obvious even then that these were all unrealistic copes. The explanation was that Rafe & Co. banally couldn't care less about world-consistency and don't waste their valuable time thinking about such things.

After that, I would argue that there could not have been any more real surprises. If an Aes Sedai could be captured, have her hands cut off, and be burned at the stake by non-channelers - multiple Aes Sedai, for that matter - then the implication is that proficiency with the One Power is a completely arbitrary quality, one that exists exclusively in service of Rafe's plot. Egwene using the One Power to escape the Whitecloaks where trained Aes Sedai could not. Nynaeve casting a radius Healing spell. Nynaeve cockblocking Machin Shin while Moiraine cowered. White Tower dropout destroying a massive horde of Trollocs while seven Aes Sedai struggled with a few hundred Dragonsworn rabble. In a world where Aes Sedai get casually captured and burned by Whitecloaks, it all makes zero and perfect sense.