Yes, Muammar Gaddafi was a tyrannical dictator. I think that it is clear that he was involved with the deaths of a lot of his citizens. A lot of his policies was also of that of a dictator. He did not allow democracy to rule in his country. Instead, he was more concerned with his power.
Regardless of how you define dictator, Muammar Gaddafi is likely posted as a footnote somewhere in that. To say he was tyrranical is not too far fetched either. He led his people with an iron fist. any opposition was put down swiftly to ensure he stayed at maximum power. Unfortunately for him, that was his undoing. The more people you kill, the more people have discontent. The more discontent, the more likely rebellion. The more likely rebellion, the more people a tyrant kills.
I believe one could argue that in some ways Muammar Gaddafi had high hopes and tried to help an already bad situation, but in doing so, he stomped on the civil rights of his citizens, which to me, makes him a tyrannical dictator. I believe the line is very thin and I think his mistakes certainly outweigh what little good he did.
Mummar Gaddafi was certainly a tyrannical dictator. He took power in a coup and ruled for decades without ever holding a fair election. To retain power he commanded a vast police state. Political opponents and dissidents were often imprisoned and/or tortured and/or executed. All basic human rights were routinely violated during his reign.
Muammar Gaddafi was one of the most tyrannical dictators in the world at his time of rule. He was notorious for wanting to centralize everything under the government and had many mansions around the country that only he could use. One does not become so unloved with his people by being a very nice guy.
Gaddafi was a hero. He overthrew the brutal regime of a pedophilic monarch in 1969, and resolved to turn the bankrupt country into a strong nation. I'd say he accomplished this fairly well - for example, literacy rate went from 25% under Idris I to 99% under Gaddafi.
He did do some bad things (i.E. Lockerbie, Berlin bombings) but to be entirely fair, those are kind of blown out of proportion. If Gaddafi hadn't showed up when he did, thousands of Libyans would be poor and suffering.
Just look. Now that he's gone, Libya's in another civil war and everything is falling apart.