Decius (201–251) instituted the first empire-wide persecution against Christians, in 250.
He did not understand the wickedness of Decius. . . . When his sovereignty was in a prosperous position and when affairs were turning out according to his wish, he oppressed those holy men who interceded with God on behalf of his peace and his welfare. Dionysius of Alexandria (c. 262, E), 6.106, as quoted by Eusebius
Decius appeared in the world as an accursed wild beast to afflict the church. Lactantius (c. 320, W), 7.302