Could a Grey Knight turn renegade?

Could a Grey Knight turn renegade?
They can't turn to chaos, and have free will. They are true warriors of big E, and the Imperium isn't the same empire the Emperor imagined ten thousand years ago. If a Grey Knight realized that this isn't what the emperor wanted, could they go renegade while still serving under the Emperor? It may be classified as corruption, but they are still serving the Emperor.

Nope.

Do people even care about the Grey Knights anymore?

Sure, people just don't sperg on them anymore.

I dunno after that whole Sister Fiasco and the memes that followed sure.

but now I mostly see nothing on these guys its like all those dudes who had armies or would post why they liked Grey Knights just disappeared

Exorcists are still baller

Not really, there just aren't enough of them and they're kept on too short a leash to develop that sort of independent thought, let alone act on it. There's what? One or two thousand at max? And they all live together in a single fortress monastery under the watchful eye of the highest levels of the Inquisition.

Yep. Probably happens occasionally, not like anything man could do to make themselves entirely resistant.

They'd get some second-long satisfaction out of their betrayal before their Killswitch gets thrown and they explode into fire or whatever, though.

Impossible.

The only thing closest to a Grey Knight going "renegade" would be if he were kicked out from the Chapter for utilizing non-standard ways of defeating an enemy.

This might happen to Alaric, the MC of the Grey Knights books (info from Dark Mechanicus to be precise).

In Dark Mechanicus, he had to fight the father of all Titans, the Castigator. He had to climb up into his insides to reach the progenitor Titan's core. As he deduced well, the Titan had a daemon for a machine spirit. Problem was that his wards didn't light up because the daemon forgot that he was a daemon after all these years. So Alaric talked with him in such a way to remind him that he is a daemon. The latter took the bait and turned daemonic allowing Alaric to defeat him. Before that his powers couldn't do jack to the daemon.

Because of this he won't be ever promoted if the GK found out about this since it's a dangerous way of thinking and Alaric seems to be a cunning Justicar, but the Inquisition would find it extremely useful.

I guess sure yeah why not. I mean its not like 40k doesn't have other bits of rather suspect lore.