The woman from Tannu Tuva was the only objective dictator everyone can agree on.
Indira not too sure. Indira ruled with a very firm hand and regularly arrested opposition members, it would be reasonable to accuse her of dictatorship.
Non-dictatorial but authoritarian one-man leaders can be found in Margaret Thatcher and Golda Meir, who basically had a cabinet system unlike their predecessors that more or less gave them full executive power willingly or in apathy.