Hmm… I’m not familiar with this guy, so I don’t know what sort of hairstyles he usually has, but I do know something about curly hair. I see two issues here: combing and lack of curl variation.
Did you use a single particle system for it? If you’re going for a natural look you may need to use more than one because Blender doesn’t offer the sort of fine control needed to represent curly hair growth variation.
Two things influence curl amplitude: location and length. The drier the hair rougher it’ll be, resulting in smaller curls. You’ll see that in the outer layers, while hair that sits closer to the nape of the neck, side of the head and behind ears tends to be wavier (smaller amplitude and frequency) for being protected from outside aggression, hence more hydrated.
Lengthier hair is heavier, so you’ll have elongated curls. The curl frequency doesn’t tend to decrease in this case, just the amplitude. It’s also worth pointing out that some curly hairs are wavier closer to the root, only forming curls somewhere from the middle to the tip. His hair looks like this type of hair.
Pixar’s Merida and Moana are good characters to train your eye to see these variations:
Merida has a very dramatic curl variation. It’s unrealistic but great to see the effect.
Moana has a more natural look. The only unrealistic detail is that the curls in the top-front of her head are more wavy while they’d be more curly irl because hair in this area is very exposed to elements, suffering a lot of aggression.
Your curl shape also seems a bit off. Natural curls form a sort of inverted cone. The longer the curl, more pronounced the effect. There’ll be fewer strands closer to the tip, and the hair itself will also thin out like this:
A. A realistic curl. B. Super thick strands so you can see the curl shape.
Once combined with the variations mentioned before:
Note that I took the opportunity created by using multiple particle systems to vary not only amplitude and frequency but number of children, because curls aren’t formed all the same.
About combing, I feel his hair is too puffed out in the top layers and straight in the inner ones. Isolated curls may flare out this way, lighter for being free of the “mass” of the hair. But all of them at the same time? Unlikely.
And his hair looks the type that sits in wavy layers, something like this:
Last observation: The curl amplitude/frequency in your portrait seems slightly too small. At this length his hair has a greater one due weight.
I hope this helps. Keep up the good work!