Synonyms of 'hardliner'
extremistDictionary, radical, fanaticUnionist hardliners warned the President he would not be welcome.
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If you describe someone as a fanatic, you disapprove of them because you consider their behaviour or opinions to be very extreme, for example in the way they support particular religious or political ideas.
I am not a religious fanatic but I am a Christian.
a former left-wing radical who was involved with the civil rights movement
Thesaurus for hardliner from the Collins English Thesaurus
The hardliners in a group such as a political party are the people who support a strict , fixed set of ideas that are often extreme , and who refuse to accept any change in them.