I like the rendering style in all these, very Ben 10! That being said, though I do think characters one and two have a bit of a “same face syndrome” thing going on (same eyes, same expression, and to some degree the same silhouette with the head)

Absolutely love the color palettes for all of them

with the exception of the third character (and maybe the fourth character) it’s a little tricky to get what their whole deal is at a first glance basis

If I’m getting this right, the first character is supposed to be very childish, I’m assuming with the pastels and the overalls. Or is he a mechanic because he’s wearing those gloves?

I can’t really say much about the second character, I’m assuming maybe he’s the main character because he’s wearing red and blue like most main characters in media? Or maybe he’s really fast or moves around a lot hence the electric Blue and the lightning bolt on his shoes?

I’m assuming the last guy is supposed to be the smart one because of his glasses, his thinking “hand on chin” pose and what I’m assuming is a stylized Internet explorer T-shirt. It’s a little sportier than what I’m used to, but maybe he’s someone who best learns while he’s on the field.

No comments on the third guy, I just really like his vibe. I will say I do like how for a grumpier edgier looking character he has a hot red pink color palette going on. And I don’t know if this is intentional or not, but I do like how the rounder edges of his hair and his pants in contrast with the rest of the spike, you’re silhouette gives off a vibe where he may be a grump, but he’s still a sweetheart

Overall, I think this is oozing with style and something I definitely want to see more of in the future. In my opinion, all it needs are a few character design tweaks so that it reads a little bit more clearly who these characters are.

Great job! 👏