My take on Dong Zhuo is a bit different to the norm.

Instead of a guffawing, morbidly-obese tyrant, Dong Zhuo is sort of a 'Start of Darkness' story where a charismatic war-hero is steadily plagued by misfortune, trauma and suspicion and steadily develops a paranoid, stratocratic mindset where he firmly believes that ruling with an iron fist is the only way to save civilisation and society's notions of wise scholars governing peacefully and justly are a lie. He absolutely despises the aristocracy and administrative class who he thinks have always spat on soldiers like him and seems intent on regressing Han culture to the level of 'Might Makes Right'. Having been a friend of Cao Cao previously and knowing that the young man has also never been accepted by the scholar-gentry class, keeps him close, much too close for Cao Cao's comfort.

We're sort of seeing Cao Cao at his most desperate because this is something he can't plan his way out of. One cannot predict raving lunacy and even if Cao Cao appeases Dong Zhuo every moment of every day, the madman may simply decide he's bored of the young man. And everyone Cao Cao loves is just as much at risk.

I'm going to deliberately base Dong Zhuo's paranoid, unhinged behaviour off characters like Colonel Kurtz from Apocalypse Now. There is definitely something of the 'Crazed Vietnam Veteran' about him.