I make a new Vegeta for Baston but these are only the portraits.
I also want to make sprite sheets

Base

SSJ

SSJ God

SSj Blue

SSj Blue Evolution

Ultra Ego

Do you have any advice on what I can improve?

Hello AleGohan2012.
It's a nice start. You should pay attention to your shadows. When lit from one side, the face is not cut in two like you did. Shadows are what makes the volume, such as the cheeks, the chin, the nose...
You should look at real photos for reference (ex: https://fr.pinterest.com/pin/24277285477262960/), or even take a photo of your face in a mirror, with the lighting you desire.

Take a look at this tutorial for starters: https://saint11.art/blog/pixel-art-tutorials/#Darkness

(I fused your four posts into one)

thanks😃

Tomorrow I will give you advice and make Vegeta normal and that too, seeing his hair the same, his SSJ blue perfect, his anger I almost liked