Comment by pierreyoda

My go-to editor was Paint.Net on Windows too, it's really good. When I switched to macOS, I found Krita which is pretty nice. I have really basic needs and Krita is free, so your mileage may vary. It's presented as a painting app on the official website (and the specialized UI looks really good), but you shouldn't be lost on the default GUI configuration. It's available on Windows and Linux too (and I just saw there's a Steam version, but it's not free).