I am surprised that no one ever mentioned Alliria. Alliria, is something of a demon though far more powerful even after she loses the majority of her power. Well she isn't really a demon she is something much older and far more powerful.
Early on she is seen smacking Spike around quite often and catches swords being wielded by Spike and Angel at the same time. She has the ability to alter time early on and even open dimensional gates. Even after she loses the majority of her power, she still has a great deal of strength and several very useful abilities.
Since I imagine a great deal of people here saw Buffy I imagine you know who Spike and Angel is but for those who don't. Spike and Angel are both vampires and have the stereotyped super human strength vampires are usually shown as having and their punches mean little more then nothing to Alliria.
