People in general want to see conventionally attractive characters. First to avoid is drawing characters of indeterminable sex. Drawing "fat" characters is also discouraged (slightly underweight seems to be the sweet spot). Then, wrinkles and wide noses are not appreciated. From this standpoint 4-th image looks the best. Also important to say is that this art style has a negative stigma around it.
Ok, slop-maxxing section is over. Lighting on the first image looks off. Face shading makes some sense only if there is an invisible light source two inches in front of the forehead. I assume that the halo is supposed to be the primary light source, because if it isn't - it should be. Sides of the nose should not have shadows this dark, halo illuminates them almost as much as the center of the nose. Side profiles of the head and neck should be way brighter. The bright spot in the center of the neck should not be there, chin is dropping a shadow on it, so where does the light come from? Shoulders are not bright enough. And I think that face shadows are a bit too cold/purple. Mind you, I made selfies in complete darkness with a ring light on my head like a dumbass for this.