Dong Zhuo
A warlord of the later Han and a notorious tyrant.
Dong Zhuo was an established general who fought against the Yellow Turbans. He rose to power by seizing Emperor Shao during a clash between court officials and the eunuch faction.
Once in power, Dong Zhuo deposed Emperor Shao in favor of the younger Xian. He was then recorded as having broken numerous palace protocols and having committed atrocities against civilians. This incited a coalition of regional warlords to rise up against him.
Dong Zhuo was eventually assassinated by his bodyguard Lu Bu.