Saturninus

Saturninus was a tribune of the plebs on the model of the Gracchi Brothers, although he was much more violent and open to inciting the people to violence.

He concerned himself in his term with finding land for Marius' veterans from the Jugurthine War and Cimbrian War.

His thuggish tendencies, and his confiscation of state property from the hands of wealthy Senators (who were exploiting the land to line their pockets) led to the Senate declaring him an enemy of the state and issuing a senatus consultum ultimum, which authorized the consuls to do whatever was necessary to defend the state, regardless of due process and habeas corpus. (As distinct from dictator, which was generally used against external enemies)

Death
Marius turned on him, and had him placed under a kind of house arrest in the Senate house, where eventually an angry mob broke in and beat he and his supporters to death.

He's remembered as populism brought about by mob violence; he was using the populist platform to promote his own ambition, inciting the plebians to open revolt against the Senate.