Rival can be a verb, yes.
For example: "he will always rival her".
Other verbs are rivals, rivalling and rivalled.
Rival is a noun--He is my rival.Rival is a verb--The brightness in her eyes rivals that of the sun.Rival is an adjective--a rival business.
The word 'rival' is a noun, an adjective or a verb.The noun 'rival' is a word for a person or thing competing with another for the same objective; a competitorEXAMPLESAs a noun: Ours is a stadium without a rival.As an adjective: They are our rival businesses.As a verb: The Thames can rival any European river in beauty.
Nemesis is a word for arch rival.
It was thought that he was being warned by a rival gang.
We play our arch-rival next week!
An arch rival or enemy might be your nemesis.
the word were is a LINKING VERB.
Opponent
Rival
The word 'be' is indeed a verb.
Yes, the word 'do' is a verb.
Verb 2. A Verb is an action word, a 'doing' word.