Tools of Characterization
Characterization in Gladiator
Clothing
A picture is worth a thousand words…so check out this picture of Commodus and Maximus.
They're both wearing armor, sure, but notice how different their outfits are. Commodus's dressed to the nines. He has elaborate armor on, colorful undergarments, and even a laurel wreath around his head. Maximus, in contrast, is wearing a simple breastplate and pale blue undergarments.
The difference is clear: the elite Roman characters (Commodus, Lucilla, Cassius) have the Roman equivalent of Versace, while Maximus's wearing simple, cheap clothing. Even though clothing gives us an idea of how far apart these guys are on the social scale, the film exploits a very potent juxtaposition: Maximus dresses simply, but in reality he's the good guy. Commodus looks great, but he's an evil, evil man.
Location
Gladiator goes out of its way to show us stunning shots of the palace where Commodus and Lucilla spend most of their time. It's full of luxury items, huge, expensive beds, incense, silks, and all kinds of other stuff. The comfortable confines of the palace contrast markedly with the dirty, squalid quarters Maximus and his fellow gladiators inhabit. Those guys live, quite literally, on the fringes—in Africa (an exotic "province" far from the center of the Empire), in the arena, and behind bars.
The thing about in Gladiator, of course, is that the guys who live in the dirt, in the prisons, and on the fringes are the "good" guys, the guys who aren't evil, plotting, parricides who want to have sex with their sisters (we're looking at you, Commodus).
While Lucilla and her son are an exception, the people who spend the most time in the palace (Commodus and his advisors) are nasty creatures, unworthy of the pleasurable lodgings they enjoy.
Speech and Dialogue
Maximus and Commodus are about as far from each other as two people could be. The former is an enslaved gladiator, the latter, a royal brat and emperor of Rome.
Even when Maximus's still a general, however, his style of speech differs markedly from Commodus. As someone who is not the emperor, Maximus must necessarily assume a very deferential tone, as he does on numerous occasions (he refers to both Marcus Aurelius and Commodus as "Caesar," and even politely refers to Commodus as "highness").
There are other differences as well. Maximus' speeches tend to be short, sweet, and to the point ("I have only one more life to take, and then it is done," for example), whereas Commodus often assumes a more verbose, "royal," tone. For example, when he's being mopey about that fact that Maximus is still alive he exclaims,
COMMODUS: This vexes me. I am terribly vexed.
One can't imagine Maximus describing his frustration by saying anything remotely like "This vexes me."
In addition, Commodus's willing to stoop to a manipulatively descriptive level that Maximus refuses. Maximus would never say to Commodus that his "wife moaned like a whore." Maximus' style of speech remains relatively the same throughout the film, whereas Commodus is willing to use words and concepts that seem to fit the occasion, which shows that he's much more fickle than Maximus…and much less trustworthy.