What is another way of saying will not be appeased?

Mollify
Deter

defiant, and other synonyms

Nevertheless, they persisted.

adamant

“Whatever they’re/you’re selling, I’m not buying.”

It depends partly on the nature of the fight you’re talking about getting into. On one level “no more Munich Accords” makes sense to those who know history and the fight that resulted after those Munich Accords appeased some powers that were hostile to Nazi Germany. But if you’re talking about two children in a minor kerfuffle, then that’s over the top.

I don’t know that it can be entirely captured in a single word but @LostInParadise ‘s adamant is my favorite.

Also:

uncompromising
inexorable
implacable
relentless
inflexible
unbending
stubborn
obstinate
bullheaded
mulish
headstrong
pigheaded

^^ He didn’t ask for a word; he asked for another way to say.

steadfastly opposed

will not be pacified?