I just took this grey squirrel photo on the off-chance, and was rather pleased that it came out pretty well. ISO25600 is far from ideal, and it has been got at by Topaz AI (which, when it works, definitely works!).
Canon R6 + RF 600mm lens
Kept dark as it seemed to suit.
Topaz does a really nice job on the noise, and it's very noticeable in the fur.
I'd like to see the whole image be quite a bit brighter, personally. It's really hard to see the detail in this.
Normally I'd agree on the lighting, but this actually matches my memory of taking the shot, under quite a bit of tree cover on a cloudy day, and I am also sometimes a bit of a sucker for the overly dark photo.
Topaz AI is very erratic, but as here, can do a good job.