He never was truthful with anyone, but always spoke and acted cunningly, yet any who chose could easily outwit him.

His character was a sorry mixture of folly and bad principles.

One may say of him what one of the Peripatetic philosophers of old said long ago, that in men, as in the mixing of colours, the most opposite qualities combine.
I will therefore only describe his disposition as far as I have been able to fathom it.
This prince was deceitful, fond of crooked ways, artificial, given to hiding his wrath, double-faced, and cruel, exceedingly clever in concealing his thoughts, and never moved to tears either by joy or grief, but capable of weeping if the occasion required it.

He was always a liar not merely on the spur of the moment; he drew up documents and swore the most solemn oaths to respect the covenants which he made with his subjects; then he would straightway break his plighted word and his oath, like the vilest of slaves, who perjure themselves and are only driven to confess through fear of torture.

He was a faithless friend, an inexorable foe, and mad for murder and plunder; quarrelsome and revolutionary, easily led to do evil, never persuaded to act rightly, he was quick to contrive and carry out what was evil, but loathed even to hear of good actions.
How could any man fully describe Justinian's character?
He had all these vices and other even greater ones, in larger proportion than any man; indeed, Nature seemed to have taken away all other men's vices and to have implanted them all in this man's breast.