Alexios V - Basileus of Basileía Rhōmaíōn from February 1204 to April 1204
Alexios V was Byzantine emperor from 5 February to 12 April 1204 during the second and final siege of Constantinople by the participants of the Fourth Crusade.

He achieved power through a palace coup, killing his predecessors in the process. Though he made vigorous attempts to defend Constantinople from the crusader army, his military efforts proved ineffective. His actions won the support of the mass of populace, but he alienated the elite of the city. He was the last Byzantine emperor to rule in Constantinople, which was sacked, despoiled and occupied, until the Byzantine recovery of the city in 1261.

After the fall of Constantinople, Alexios V was blinded by another ex-emperor and later executed by the new Latin regime in the city.
Alexios V
Emperor Alexios V of the Byzantine Empire