Lotor…I really don’t want to go into my full rant again, but he deserved so much better. Also Allura. She lost her family, her entire race, her planet, and then, after giving everything she has to save the universe, she just dies???
Kolivan because all he wants to do is stop the galra but all he gets is cold shoulders and his agents brutally dying including his right-hand man Antok. He get captured and chained to the ceiling for two years by Macidus whilst his remaining blades got massacred