Which emperor's assassination set off the crisis of the third century

Alexander Severus

Explanation: The assassination of the Roman emperor Alexander Severus in 235 was the beginning of what was known as "The Crisis of the Third Century" which lasted 50 years. It was a period of political and economic pressure inside and outside the Roman empire. It finished with the ascent of Diocleciano in 284.

no one really purchased it themselves, it was all america, they had debates etc.