Yes. The same as the greek or hindu pantheon of gods exists. Or that you and I exist talking here. But do you really wish so hard that Lucifer exists? Then we get back into who is to BLAME for our problems.
Is this powerful negative entity an external source? If we believe that then we give our power away to it. If it is within us then we empower ourselves and will have to make the choice to be Aware or remain sleeping. Most religions cover up that latter fact.