This review highlights the effective design criteria for lanthanide single-molecule magnets, which show strong magnetic blocking temperature up to 60 K. Increase in the anisotropy barrier and decrease in the quantum magnetization are attainable by controlling the ligand field, local molecular symmetry related to the coordination geometry of the complex, and magnetic dipole-dipole interactions between the lanthanide ions. With recent advances in this field, a new 2-coordinate complex, which is predicted to show a blocking temperature of more than 77 K, is also introduced. The existence of a proton in the nitrogen atom of porphyrin ligands quenches the single-molecule magnet because of the destruction of the symmetry, which can be possibly overlooked because of the disorder of the position of the proton in the crystals.