deuteragonist
Concise Oxford English Dictionary © 2008 Oxford University Press:
deuteragonist /ˌdjuːtəˈragənɪst/
▶noun the person second in importance to the protagonist in a drama.
– origin C19: from Gk deuteragōnistēs, from deuteros ‘second’ + agōnistēs ‘actor’.
'deuteragonist' also found in these Oxford entries:

