I've tried GIMP a few times but don't find it very user-friendly. It's very powerful, but with a steep learning curve.
I've never tried GIMP, mainly because I've read quite a few comments such as this - and the screenshots I came across did look a bit intimidating.
Affinity Photo is like an imitation of Photoshop, but not as many features
Photo restoration tutorial: https://www.youtube.com/watch?v=OwRVtGedxyg
It has a one-off cost of around $100.
I got Affinity v.1 on a special offer, attracted also by it being a one-off purchase rather than a subscription, and it's the program I use if FastStone doesn't quite cut it. Affinity v.2 is now out, but for me I'm not convinced it's worth the extra outlay at present.
I've tried Paint Dot Net (the volunteer successor to MS Paint) from time to time, but never quite got to grips with it, though it does have a lot of optional add-ons and I suspect it can do quite a lot if pushed. If I ever find I can't use Affinity v.1 for any reason, I'd certainly reconsider it.
Back to FastStone - yes, it does do red-eye removal and a lot of other kinds of edit. Full details are at
https://www.faststone.org/FSViewerDetail.htmIf you follow the Download link you'll see that there's a portable version available. You can run this from a USB stick without installing anything, so it won't affect any of your Windows settings - it might be a good way to try it out. No registration is needed, even for the installed version, though donations are accepted.