Look for a trunk line and shape. Many large, upright branches seem confused so I'd be looking to simplify the shape, probably by removing a couple of those strong upward branches. Without seeing the tree in 3D I would not like to pick because small nuances can have a big bearing on shape and flow.
The growth appears to indicate a dwarf variety which may explain some of the lack of vigour but I would also be looking at care, position, etc to try to get better growth before doing much further work.