Addendum

As a follow up to "Nitpickyism," here are my picks for worst theological invention ever:

1. Gnosticism, i.e., God only speaks to special people in private.
2. Deism, i.e., God is not intimate with His creation (which rules out the Incarnation).
3. Monotheism (Islam), i.e., God is one (as opposed to Trinitarian, i.e., God is three in one).
   
4. Atheism, i.e., God is not. I don't know how much worse you can get.