Poor for many years and suddenly growing rich, he could but ill conceal the change in his fortunes, indulging without moderation the appetites which a protracted poverty had inflamed, and, after a youth of indigence, becoming prodigal in old age.
His Book I Chapter 66: Revolt of Vitellius. Vienna

A man of foul and infamous character;
His Book II Chapter 30: Otho versus Vitellius. Caecina and Valens

He was a man of loose character, but of no small ability, who sought to gain by profligacy a reputation for elegance. In the theatricals performed by young men during the reign of Nero, at first apparently from compulsion, afterwards of his own free choice, he repeatedly acted in the farces, with more cleverness than propriety.
His Book III Chapter 62: Vitellius versus Antonius Primus. Valens put to death

was so rapacious, that neither what he plundered from enemies nor what he stole or got as gifts and bribes from his friends and allies could satisfy his wishes.
Plt Otho Chapter 6: Otho versus Vitellius; the siege of Placentia