mainly proportions and basic strutes are messed. face shape for example doesn't follow any kind of "regular"(not to say normal) skull structure, and instead looks more lke a mass of meat compressed together. look at a mirror and you'll see that faces always follow the same lines, wich are created by the fact that they are over a skull. same for hair, wich is aligned with nose but doesn't connect to the head as it looks like pasted from somewhere else, and one of the most important things is that your light color used for shading does not work. is not that shadows have to be always black colors, but for this specific case, it is not a second light souce and ist not helping to increase the volumen and features of the face, and rather blends and trns everything weirder.
Its basic anatomy. use a reference to guide yourself. its easier than it sounds
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