>>106278599
>>106278843

Here's my best shot to fix the anti-aliasing issue:
>start with Krita and open your image (I used your original provided in the thread)
>image -> scale image to new size (128x128 -> 1024x1024) + filter type is set to "nearest neighbor"
>put it into flux and remove any garbage outlines (I had to tweak the prompt a bunch but I got this to work: "keep the characters exactly the same, clean up the outlines so they are only black, there should be no peach outlines, remove any excess incorrect outlines by turning them into background")
>I run the output image through flux a second time, this time to convert the background to solid green
>Krita -> image -> scale image to new size ->256x256 then ->128x128 (the 256 in the middle helped a little with the outlines)
>"Filter -> Colors -> Color to Alpha" (as in my previous post)
>export image as PNG with Alpha channel for transparency and no HDR

The outlines on this one are a little thicker but that was flux trying to clean up any unwanted outlines like the peachy color outside the characters model. The character is a lot clearer than my last attempt and a lot "less" anti-aliased (at least on the inside) but still has blurry outlines. Honestly, the best strategy might just be using magic wand tool to select the outside, then using a straight edge cutter to clean up the outlines. It will be more consistent and probably faster too (at least on pixel art) than my method. I tried a workflow where I simply added a bunch of yellow background to the original image until it was 1024x1024 in size, but the characters remained the same, however Kontext kept blurring the characters.

This is the best I can do with my crappy workflow. The only time I can see this helping is if you have to do very large sprite sheets. I think the best strategy is just magic wand tool with a little clean up by hand. Hope you find a good solution that works for you, good luck.