A word or phrase for 'enemy of faith' [closed]

How about "sectarian foe"? I think that's appropriately ambiguous - it doesn't carry strong connotations of being a label that Christians would apply to pagans. It's not a single word or a set phrase, but I think that may be OK or even an advantage, since the set phrases will tend to lack that ambiguity.

Alternatively, you could just calque it to "faith enemy". I actually think that might be clearer than "enemy of faith".

One word is infidel:

[Merriam-Webster]

1 : one who is not a Christian or who opposes Christianity
2 a : an unbeliever with respect to a particular religion
b : one who acknowledges no religious belief
3 : a disbeliever in something specified or understood

It doesn't promote the idea of an active enemy, however, at least not in its dictionary definition. (Although popular media seems to have promoted the idea of infidels as barbarians.)

For that, iconoclast might be more appropriate—if used in a religious context:

1 : a person who destroys religious images or opposes their veneration
2 : a person who attacks settled beliefs or institutions