deuteragonist

[doo-tuh-rag-uh-nist, dyoo-] /ˌdu təˈræg ə nɪst, ˌdyu-/
noun
1.
(in ancient Greece) the actor next in importance to the protagonist.
Origin
1850-55; < Greek deuteragōnistḗs. See deuter-, agonist
British Dictionary definitions for deuteragonist

deuteragonist

/ˌdjuːtəˈræɡənɪst/
noun
1.
(in ancient Greek drama) the character next in importance to the protagonist, esp the antagonist
Word Origin
C19: from Greek deuteragōnistēs, from deutero- + agōnistēs contestant, actor