According to Protestant Theology is there any ‘common denial’ that would group all heretical forms of Christianity under one?

I know there are many splinters of different churches after the reformation, some that seem to be different kinds of Christians and some that seem to be opposed to the previous Christians, while still taking the name ‘Christian’. Of all these false splinters (as viewed by the originals) they also obviously disagree with each other on important matters, otherwise they would not be a separate group. The question ‘is there any unity or common reformed doctrines that they all deny?’ In other words are there some basic doctrines that the Protestants hold that separate them from what they would call ‘heretics’ without having to go into the details of each splinter groups favorite topics? A sort of short-cut if you will that groups them all together in a more direct fashion. Or are they holding a whole host of differences without a common root that makes it impossible to form such a simple grouping?