Parallel relationships

Coriolanus and Aufidius's relationship and the batman and joker's relationship are parallel. Both relationships are rivalries, yet both characters also have distinct similarities in their characters. Coriolanus and Aufidius are almost like the twin of each other, with a few differences. For example, Coriolanus and Aufidius both express traces of honor and policy yet individually they favor one quality over the other.
"Coriolanus practices policy in warfare but not in civil affairs; Aufidius uses policy in the court of the Volscians but not during battle." pg.5
However, they still contain the same flaws of pride, defect of judgment, and an inalterable austerity of manner. Their identities, strengths, and weaknesses are extremely similar and they are able to perceive in the other, the traits the each possess. However the manner in which they act on these traits differ, which consequently results in different consequences.
The Batman and Joker are also alike and have the same genetic disposition for greatness. However, they both end up in opposite directions because their differing environmental influences experienced in childhood. They are complimentary contraries; the yin and the yang. However, in both situations, the relationship experiences an imbalance and one becomes superior to the other. This will lead to the inevitable downfall to one of the characters.