What is the word for a person who thinks/afraid others can change them? [duplicate]

Solution 1:

Three words come to mind. Two nouns and one adjective that might conceivably be used as a noun.

Fanatic = person who has very extreme beliefs that may lead them to behave in unreasonable or violent ways

Cambridge dictionary

Diehard = someone who is unwilling to change or give up their ideas or ways of behaving, even when there are good reasons to do so

Cambridge dictionary

Obdurate (adjective) = 1a : stubbornly persistent in wrongdoing. “an unrepentant, obdurate sinner”

1b : hardened in feelings “The obdurate enemy was merciless.”

2 : resistant to persuasion or softening influences

Merriam Webster

Of the three I feel that fanatic may suit best where religion is relevant, diehard in more general or secular cases. It may sometimes be possible to use obdurate as a noun but only as shorthand as in “An obdurate man” = “An obdurate”

Solution 2:

I suggest zealot, which Merriam-Webster defines as—

a zealous person

especially : a fanatical partisan

There's also this word (adjective) for such people—

dyed-in-the-wool

Thoroughgoing; out-and-out: a dyed-in-the-wool populist.