Lord Sovereign
The resident Britbong
And/or antagonist, I might add.
For me, it is power. Not so much in overwhelming, god like power, but power that is proportionate to the story. The villain should have power, if not direct power over the protagonist, and exert it competently and consistently. Through this their influence is made known to the audience and builds up their threat value whilst giving a very real obstacle for the protagonist to overcome. Even in boring real life, someone with power who knows how to wield it is a very dangerous person and the same principle applies to fiction.
TL;DR, there can be no threat without power and its thoughtful exertion.
For me, it is power. Not so much in overwhelming, god like power, but power that is proportionate to the story. The villain should have power, if not direct power over the protagonist, and exert it competently and consistently. Through this their influence is made known to the audience and builds up their threat value whilst giving a very real obstacle for the protagonist to overcome. Even in boring real life, someone with power who knows how to wield it is a very dangerous person and the same principle applies to fiction.
TL;DR, there can be no threat without power and its thoughtful exertion.