If excess pride causes Coriolanus' downfall, then he's a lot like a whole laundry list of tragically flawed heroes that have come before him. Seem plausible.
Pride goes before a fall, and it definitely went below Coriolanus', right? After all, if Coriolanus weren't so arrogant, the plebeians would totally love him and elect him to consul instead of screaming for his blood when they riot in the streets of Rome. Right? Eh, maybe. It's true that Coriolanus is an obnoxious jerk and a class snob. But there are plenty of other reasons the guy went down—like his freaky relationship with his mom (see "Themes: Family"), his inability to keep his mouth shut (see "Themes: Language and Communication"), and/or his sense that he's not a real "man" unless he's aggressive and violent (see "Themes: Gender"). In Coriolanus, there's no shortage of reasons to end up stabbed in the back.
If not for his excessive pride, Coriolanus would have been elected consul and would have lived happily ever after in Rome.
Coriolanus may be proud, but it's his twisted relationship with his mother that causes his ruin.