Bad drywall job or water damage?
Appears to be a very substandard mud (drywall compound, thus, drywall joint) job, probably put on without waiting for each layer to cure, possibly also poorly reenforced, thus the cracks. The "Visible hump" is from lack of skill or care in properly feathering the joint.

Question will be whether this is the best the builder can manage, so having them do it over is pointless (as that's certainly sub-par for new construction) or whether you say the heck with them and fix it right either yourself, or by hiring someone actually competent. You might also want to take a harsh, glaring light to other drywall surfaces in the home to see if this is really the only bad spot.