In what way is he dictator if he can be challenged and defeated in the courts? FWIW the Wikipedia page, on cursory view, only refers to him as part of political parties and having been elected: perhaps you can flesh it out a bit for someone not familiar with Singaporean history, thanks.

His party is a ruling party of Singapore since before independence, until 80s it won all seats in parliament. He was a prime minister for 30 years, current prime minister is his son.

Lee Kuan Yew was a benevolent dictator, except for his political opponents. Dictatorship is a spectrum :)