hard-boiled vs hard-bitten

hard-boiled and hard-bitten both are adjectives.

Word	Noun	Adjective	Verb	Adverb
hard-boiled	No	Yes	No	No
hard-bitten	No	Yes	No	No

As adjectives, hard-boiled and hard-bitten are synonyms defined as:

Other synonyms of hard-boiled include pugnacious.

hard-boiled (adjective)	hard-bitten (adjective)
(eggs) cooked until the yolk is solid	tough and callous by virtue of experience
used of persons; emotionally hardened
tough and callous by virtue of experience