"You have a disease" Lucious Vorenus to Mark Antony
"And It is the same one I have"
What exactly is he referring to here? I struggled to find this parallel between the 2 characters, who commit wrongs for totally different reasons.
I think he's talking about how their ambition swamps their sense of right and wrong. Their sense of ethics is weak and brittle. As John Huston put it in Chinatown,“Under the right circumstances, a man is capable of just about anything."
shareAntony willingly enjoyed a debauchery like stupor, connived his way to steal and cheat those closest to him, and in general his ambition was just a way to stroke his ego as opposed to the good of Rome (unlike Octavian).
Lucious carried out his orders and duties as a soldier, didn't cheat on his wife while he was married, and didn't want more than to live a simple life with a loving family. Killing was a way of life for a soldier back then, outside of that his sense of right and wrong was quite steadfast.
To me, they are completely different people.
I see what you mean in that Lucius is very stoic and honorable in his duties, whereas Marcus is more carefree and dishonorable.
I think that when Marcus said the quote mentioned here to Lucius, he was simply talking about "ambition", they both suffer from the disease of ambition.
Remember how proud Lucius was at each of his promotions throughout the series. Early on when he retrieves the golden standard for Caesar and is promoted to 'primus pilus' (senior centurion), and then later when he is promoted to 'praefectus evocatorum' (or Evocati), and then he is asked to become a magistrate, and finally promoted to a Senator. In some cases he does so grudgingly, but in most cases it seems he is hesitant due to lack of confidence or understanding of the position (in regards to the magistrate/Senator positions anyway) but ultimately embraces them and then becomes very proud. He also mentions many times throughout the series the pride he has for the Vorenus name and status.
So while Lucius and Marcus are very different types of people with very different values, they are both extremely ambitious and sometimes do things that put themselves at risk in order to pursue that ambition.