"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.
Though the comic also features Nale and Kubota, two Big Bad Wannabes, a Dragon who is in some ways even more dangerous than his boss, an Eldritch Abomination that hasn't done anything yet but could destroy the universe if released, the Magnificent BastardEvil Overlord who's also a main character's father, and a trio of fiendish Chessmasters who are playing everybody else to a greater or lesser extent — so there's definitely more than a bit of a Big Bad Ensemble going on rather than just Xykon. As he's arguably the most powerful non-divine villain in the comic and is the most central single villain to the plot, he'd still qualify as theBig Bad though, barring a (not entirely impossible) future upset.
Recent developments as of #830 mean this might be more of a Big Bad Duumvirate between Xykon and Redcloak, with each thinking they control the other.
Sluggy Freelance: Hereti Corp and K'Z'K constantly take turns being the overall Big Bad of the comic. Other examples (mainly for mini arcs) include vampire queen Lysinda, demon general Lord Horribus, corrupt nobleman Sir John Jacobs, and a totalitarian dictator known only as "His Masterness".
Though His Masterness turned out to be a subversion. It was originally Alt Doctor Shlock keeping the people of 4U city in drugged stasis while he repairs the damage caused to the Dimension by his irresponsible portal abuse, then the role was assumed by Alt Riff who continued the job after Shlock's death, and then by a computer Riff left in charge of the city, while he devoted all his energies to saving the world, that ended up going rogue.
The Law of Purple: Silver, Lord of Caligula.
Adventurers!! played around with this, even having a PR war between two of the villains over who was going to be the Final Boss.
Bob and George had a new big bad each year, though Dr. Wily would always come up and Bob stayed consistent.
Year One: The Yellow Devil who undergoes a Heel Face Turn and becomes Nate
Bob could be considered the Big Bad too.
Year Two: Mynd
Year Three: Megaman
Year Four: The Helmeted Author Who was the Man Behind the Man in year three
Year Five: Non-Alternative Mynd (though Bob comes in a close second)
The Life of Nob T Mouse: The Pie Ghosts of Somewhere in Pie Noon and probably also King Nastie from the Nasties stories, although he's also something of a Dragon.
And let's just stop saying that the Light Warriors, either individually or as a group, are Big Bads, because they're not - they're working for Sarda and he is the Big Bad.
Ansem Retort's Big Bad tends to change every season.
Season 1: The FOX president.
Season 2: Cloud for the first half of the season.
Season 3: Cid.
Season 4: Xemnas
Season 5: none, as the season focused on Axel and Aerith's wedding.
Season 6: Xemnas, Ansem, and oddly enough Belle are competing for the Big Bad title this season.
Season 7: Xemnas again, and it's hinted that there is another
Oddly enough, Vriska can count as the Big Bad, if taking the description of the trope very, very, literally.
Taking it more directly though, Lord English is the Big Bad; Doc Scratch has done everything for him and he is the Man Behind the Man to Vriska.
His actions also led to the creation of both Doc Scratch, allowing him to enter the universe, and Bequerel, allowing Jack Noir to gain first guardian powers. He is also in charge of Betty Crocker.
Really, until we reach the end of Act 7, we will still probably have no idea who the Big Bad is.
With this pageVoodoo Walrus seems to be setting things up to suggest that Rip Flintolocke, a character who hasn't even been seen beyond being a shadowed figure, is responsible for everything that's happened in Grymm and Creepknight's lives.
