GBSprite

Great at emulating the iconic style of Game Boy-era pixel art sprites. The model's sprites are certainly capable of being used on their own or as a starting point for cleanup.

I have yet to try this, but Pixel Perfect AI Art Converter could likely be coupled with this for very good results. You can find that here, if you're interested:
https://github.com/nygaard91/Pixel-Perfect-AI-Art-Converter?tab=readme-ov-file