The most nearly opposite word to "liege" would be "servant" as a liege is someone who owes loyalty to a superior, whereas a servant is someone who serves others.
Cowardice is nearly the opposite in meaning of valor.
Synonyms are words that have the same or nearly the same meaning.
Rebel.
"Asserts" or "claims" are phrases that are mostly nearly the same in meaning as "avouches."
The knight knew how to say a tongue twister. Practice and familiarity with tongue twisters could help improve one's ability to say them smoothly and quickly.
Servant
Cowardice is nearly the opposite in meaning of valor.
Synonyms are words that have the same or nearly the same meaning.
of Delay
Leniency
Smooth
Defeated
dawdle
Rebel.
immoral, unethical
Sinful.
Words that are opposite or nearly opposite in meaning are called antonyms.Examples are big and small, or long and short. Not all words have antonyms.When two antonyms are used together for effect, it is called an oxymoron.(see the related question)