Hinduism does not believe that there is a God and that there is a Devil. There is only God.
The iconography and symbolism of the image of Goddess Kali has great importance. The positioning of the female form over the male form is of particular importance.
In the case of Bhagavan Narasimha, we see that Goddess Lakshmi is sitting in his lap. In the case of Bhagavan Vishnu, we see that Goddess Lakshmi is sitting at his feet. We do not see a feminine form other than Kali standing on top of a male deity. And who is that male deity? Shiva, the mendicant.
Shiva is a sadhu. Shiva is the deity of all sannyasins. His marriage too is the highest demonstration of renunciation in the world. Because he does not bother about where he stays, he does not bother about what he wears, he does not bother about what he eats, and he is ever-blissful. That is why he is the Bhagavan of the sannyasins.
In Sanatana Dharma, everything is deified. Sanatana Dharma does not have any dichotomy of divinity. What is dichotomy of divinity or duality of divinity? It is the belief that there is something divine and that there is something that is not divine. That there is a God and that there is a Devil. Sanatana Dharma does not believe in that. All the traditions of Sanatana Dharma profess that everything that we see is the manifestation of the One divine principle and so there is no problem worshipping Kali, because Sanatana Dharma has deified destruction and death.
In some regions of India, Kali worship is prohibited for the householders. However, in some other places in India, Kali is worshipped daily in several homes. Same is the case with the worship of Chinnamasta. Kali is the deification of the terrible. Even the word ‘Kali’ could denote the terrible. Kali is the terrible or terror incarnate.
Source - Prabuddha Bharata January 2016 Issue - Editorial page 12.