Big Bad / Web Comics

"I mean, I already 8eat a last 8oss! The 8lack king was the officially sanctioned last 8oss of our session, and I killed him. This is different. There's always someone stronger w8ing to 8e revealed. Jack showed up shortly after that, and he was MUCH stronger. Eventually the curtains get pulled 8ack, and you find out who was 8ehind every terri8le thing that happened all along. Someone who is invaria8ly stronger than all other adversaries 8y a wide margin. The supreme villain! To 8e honest, I was always kind of w8ing for that guy to show up, whoever he was. For the other shoe to drop, you know? There's always a 8ig 8ad 8ehind everything."

"The ultimate villain of the story, who's causing the problem the heroes must solve."

Note that Big Bad is not a catch-all trope for the biggest and ugliest villain of any given story. The Big Bad is the one who turns out to be behind several other seemingly independent threats.

http://tvtropes.org/pmwiki/pmwiki.php/BigBad/WebComics