Which complex has square planar structure?

In [Cu(NH₃)₄]²⁺, the oxidation state of Cu is +2 and the 3d-subshell has 9 electrons. As ammonia is a strong ligand, it moves the unpaired electron from 3d and placed in last orbital of 4p of Cu. In this way, the complex achieves dsp² hybridization and complex has square planar geometry.