Antagonist
Character Role Analysis
Christine Mannon
If Lavinia has an enemy, you had better believe that it's Christine. There isn't a single Mannon in Mourning Becomes Electra who doesn't have blood on their hands—even Ezra, who killed who knows how many people in the Civil War. Still, that was wartime, and Lavinia and Orin never would have killed in the first place if not for some desire to punish the evil-doers.
Christine, on the other hand, murders Ezra because she's bored with him and never really loved him. She was actually hoping that he'd die in the war so she could inherit his money and run off with Brant. Combine that with the fact that she's cheating on her husband with his nephew (feel free to take a moment to gag) and has no guilt about that whatsoever, you've got one bad girl. She's the obstacle in the way of the family justice that Lavinia would very much like to serve up.
Adam Brant
We're not trying to be too harsh here. It was totally traumatic that Adam's father was disowned because he had a thing for a lovely young woman named Marie Brantôme who also happened to be a servant. It's also a bummer that Brant had to struggle to keep from starving and to get to where he is as a result. It's natural to be ticked off about something like that. Still, that's no reason to try and ruin an entire family. Brant's a vengeful guy with murder on his mind, and he's not above toying with the emotions of other characters like Lavinia to try and hide what he really wants: her mother. Christine hatches the plan and gives Ezra the poison, but Brant is just as much to blame for Old Man Mannon's death.