The scaling algorithm to use is LoHalo.
quote: LoHalo method: when you downscale an image thats less than a half of the original size
It looks to me that the MSPaint scale also incorporates an automatic degree of sharpen. As a comparison.
(1) Scaled with Gimp 3.0.8 LoHalo
(2) Your MSPaint example. I can see a small amount of "fringing" that forehead detail for example.
(3) A default value unsharp mask applied to (1). There are other (possibly better) sharpening tools, I often use one of the gimp_gmic_qt filters.
quote: LoHalo method: when you downscale an image thats less than a half of the original size
It looks to me that the MSPaint scale also incorporates an automatic degree of sharpen. As a comparison.
(1) Scaled with Gimp 3.0.8 LoHalo
(2) Your MSPaint example. I can see a small amount of "fringing" that forehead detail for example.
(3) A default value unsharp mask applied to (1). There are other (possibly better) sharpening tools, I often use one of the gimp_gmic_qt filters.