There is a strong argument that but for the existence of tyrants humankind would have gone extinct before written history. They allowed humanity to evolve and flourish as the social creatures we are today.
While a tyrant does suppress freedoms, and costs lives (in both subjects and opponents) what they provided was stability and strength for the community. This stability enabled ALL discoveries up until, and including democracy. Set aside the luxury of contemporary morality when examining history to understand all its complexities.