Looks high to me too. Don't you need retaining walls properly engineered if they are over a certain height?
Am I understanding right, there's a section at the back of that side which adjoins a different neighbour and that section is correctly done? Actually it looks a little odd. There are two different types of fences at that back corner. The back fence looks higher than the fencing around the jutting out part. And who erected the section of fence that comes back in to the existing wall?
Just to confirm, who changed the level? Did the lower neighbour cut into the slope?
I presume that fence is the builder's temporary fence?