A couple of dictionary checks suggest some set of:
- Ruler who is unrestrained by law or constitution
- A usurper of sovereignty
- Ruler who uses power oppressively or unjustly
Obviously b) is not applicable as per GP. He has also been constrained by the supreme court and others multiple times in this term, which suggests a) is a stretch. c) probably a fair accusation, though I'm not sure I would agree.
Hitler was not elected Chancellor by the German public. Germany had/has a mixed-member proportional system, meaning that coalitions may form after everyone votes President Paul von Hindenburg appointed Hitler as Chancellor on 30 January 1933 after negotiations among conservative politicians who believed they could control him. The Nazi Party was the largest party, but it won only 33.1% of the vote in the final free Reichstag election of November 1932 and never secured a popular majority. Once appointed, Hitler exploited emergency powers and political intimidation to dismantle democratic institutions and convert his government into a dictatorship.
During his political ascent he used his Brownshirts - a large, organised paramilitary force - to assault political opponents, break up rival meetings, intimidate voters, and fight street battles, helping destabilise the Weimar Republic and suppress opposition.
Your comment implies that Hitler seized power despite a lack of popularity. The historical record shows that Hitler was wildly popular in Germany, even up to the end of WW2.
I very clearly provided the exact percentage popularity he had at the height of his democratic rise. Whether you'd like to accurately call that less than a third, or "wildly popular" is I suppose subjective.