Xerek (pronounced zer-ick) is a villain who was supposed to be the main antagonist in The Incredibles, but was replaced by Syndrome due to the latter's popularity among the producers.
However, Xerek is now being used in the Boom! Studioscomic book series as the villain of the ongoing story and being revealed as an ex-boyfriend of Helen's back in the old days, though having become decrepit from accelerated aging of a currently unknown source. Leading The Unforgivables, a new league of supervillains, Xerek's goals at the moment involve both taking out the family in addition to world conquest.
Cold and calculating, Xerek is apparently known and feared by superheroes and villains alike. Though very little of his personal life is known, Xerek has an unhealthy obsession towards Helen Parr, who had dated Xerek for a time but broke up upon learning of his villainous activities. Despite this, Xerek still pines for Helen and seeks to prove that her current life as the wife of Mr. Incredible is a complete waste compared to being with him.
The Incredibles comic book
Xerek fist appears as the main villain of the "Lies and Secrets" story arc by hiring Bomb Voyage to make the Eiffel Tower vanish. After capturing him (with help from Mirage), Elastigirl interrogates the villain and is led to Xerek, who invites her to sit down with him for dinner. Despite his attempts to convince her to come back, Helen refuses to have anything to do with Xerek and he summons armed guards to capture her. However, Mirage arrives with the guards and gets them to capture Xerek instead by promising them better pay. After being sent to prison, Xerek quietly descends into a hidden chamber, where his self-formed organization of villains The Unforgivables wait for him to lead them to victory.
In the final story arc "City of Unforgivables", Xerek enacts a master plan to destroy the reputations of the Incredibles. Using Mezmerella's hypnotic power and amplifying it with a machine powered by the disembodied brain of the deceased superhero Everseer, Xerek is able to command the people of Metroville to hate the Incredibles. He then sends a giant Incredibles-themed robot piloted by The Underminer to attack the city in the heroes' name, further destroying public opinion. Though the robot is destroyed, it does nothing to save the Incredibles' good names and they are forced to walk away in shame, while Xerek is victorious. What comes afterwards remains unknown due to the title's abrupt cancellation.