Which people were most likely to be accused of witchcraft?

Answer

Christians, enough said. I don't wish to be mean to Christians, but it's the truth. A large number of religions accuse (read persecute) witches, the inquisition certainly tipped the scale toward Christians, but you are forgetting such diverse groups as the Hopi and several other Native American tribes, East Indians (see link below), several tribes in Africa, Jews and Muslims.

Please note, in most (but not all) cases the definition of "witch" tends to be one who does ill toward others, but all such definitions can be interpreted to the views of the persecutor.