Not good at statting out stuff, but I've got a few suggestions for those that are.
Imp (Higher Defense, Lower Strength, Average HP, Decent MP, Special Attack: Poisoned Stinger) around 8th level?
Displacer Beast (Higher Defense, Average Strength, Average HP, Low MP, Special Attack: Tentacle Slap) around 13th level?
Earth Elemental (Average Defense, Higher Strength, Higher HP, Low MP, Special Attack: Crush) around 20th level?
Fire Elemental (Average Defense, Average Damage, Average HP, Higher MP, Special Attack: Burn) around 20th level?