Answer:
Justinian's best accomplishments is that he married well. Justinian's original attraction to Theodora may have been her beauty, but it was not very long for him to respect her political abilities and intelligence. His wife was a savvy politician in her own right. Justinian treated her as her intellectual equal they ruled the Empire together. Theodora even saved the throne in 532 when a riot threatened to overthrow Justinian.
Justinian and his court were to flee the city in exile when Theodora's impassioned plea to fight where heard. The rebellion was easy to put down, then Justinian remained emperor. As emperor, Justinian made excellent reforms in the areas of law, urban development, and conquest. His Justinian Code curbed bureaucratic corruption in the Empire for centuries. Theodora was a partner in these reforms and convinced Justinian to reform the roles and responsibilities of women in the Empire.
His willingness to promote Theodora's talents and allow her to have a voice on his court should be considered one of his best accomplishments. Theodora was responsible for establishing royal decorum in the court that further legitimized the authority and respect of the crown. Justinian himself would credit Theodora for her guidance and leadership in these realms.
