Characters that were already humanoid being depicted as human. This can include dolls, androids, furries, humanoid robots or mecha, and monster humanoids, with any non-human traits like doll joints, obvious mechanical features, fur, horns, wings, impossible skin colors, etc removed. Since impossible hair and eye colors are already commonplace in anime depictions of regular humans, those features do not need to be removed to qualify as humanization.
For example, consider post #1234238 versus post #1477667. The first image has her with doll joints, while the second one has her as a regular human. In this case, the second image would be tagged as humanization.