User blog comment:EmpyreanSmoke/Strength scale/@comment-4762882-20140806110033/@comment-3481504-20140811103840

Eric Kripke himself confirmatively stated that "you don't get much higher than her without digging into archangel territory," meaning she's the strongest demon that can ever be created in supernatural. Alastair could definitely wrestle around with Cain for a while, but Cain could just smite him if he got the chance. If an archangel used his powers on a Leviathan but from Pluto, he could completely bust Leviathan into vaporization. And Eve said she's older than Castiel which is not nearly enough evidence to jump to the conclusion that she's stronger than archangels.