who is the flat character in the Pearl

I think the periphery characters all get less complex as you move outward from Kino and Juana. Their baby Coyotito is, of course, flat but the infant works as a vehicle to bring out the multi-level traits in his parents. If we recall go by definition, it would be safe to say that the dealers and the trackers are pretty one dimensional. They are only after profit. The priest and the doctor seem flat but if we are to take them within the context of colonial influence and attitude, they become a little more interesting. The other relatives have enough going for them to keep them round. Their experiences are reflections of our protagonist's. There is more to interpret about them than simple monikers.