This thread has been interesting because to find a heretic, I first have to define heresy.
I don't think theological difference, which there aren't. Calvin and St. Thomas Aquinas both agreed on predestination and election.
Free will is really the issue. Aquinas admits man's will is limited by circumstance beyond his control (providence). He admits to Romans and to (
Jeremiah 10:23): "The way of a man is not his: neither is it in a man to walk." However, Aquinas seems to be saying the man's will is subject to cognitive power, or conscience so the will is subject to reason. We can know good and evil through reason when it is guided by the Holy Spirit but we don't, alone, have the power to enforce our will. Reason alone can also lead us astray, as we are fallible. And there is a difference between "natural will" which is unregenerate and the regenerated will, infomed of the Holy Spirit.
However there is heresy,
Just my short list:
1) The devil made me do it. I am a helpless victim
2) I had to attack and/or kill that person because he had a devil or he was a heretic. I am saving the world or him or something
Both of those are anathemas 1) The devil can seduce but the devil cannot compel 2) That is self evident why it is an anathema. We should not commit the sin of hurting or murdering anyone to save the world or other people from what we declare are "bad ideas"
JMHO