I was recently looking up something about lashon harah, and on Erchin 15A, Rav Yosi ben Zimra says that anyone that says lashon harah it is as if they reject everything, and I know I have seen similar things in the Gemara before (references escape me).
Is there a list of things about which the Gemara says one is "kofer b'kol"?
The motivating example for this was lashon harah, where someone was saying it's "not so bad" (i.e. some people seem to treat it with far more importance than other mitzvot that are "more clearly deorita" (not talking about "lo telech rachil" here)), and the Gemara seems to claim it's as bad as killing people. This list would show either (if long) that it's mostly hyperbolic, and it's just a way of saying that it's bad, or (if very short) that it is in a rather small group of very important mitzvot that really are equivalent to murder.