Is there an idiom that allows you to express this idea? I am either trying to find an idiom, or a word, or an adjective that I can use in a phrase during a casual conversation. As long as you manage to convey the idea in a good-sounding way, I would be okay with anything.
The only way I could express this is the following way:
This guy would not give any inch, and is ready to die for it.
The above doesn't sound too idiomatic and the "it" may be a bit ambiguous.
Best Answer
You might be looking for perfectionist, overachiever, or hard-liner for a noun.
Uncompromising would work as an adjective.
As for idioms, this could work:
Different words would be used in different contexts; for example, a "hard-liner" is usually used in reference to politics or other ideological stances. The point of view is also very important, as "hard-liner" is typically used to describe someone you don't agree with and/or criticize rather than one of your allies or friends.