How many TV shows has Ted McGinley purportedly been responsible for "killing"?

Not necessarily a show killer. Many of the shows he appeared in brought him in as the show was losing popularity. He did have a successful stint on " Married With Children " as well as a few other relatively successful roles.

From site:
McGinley has been called "the patron saint of shark-jumping" by jumptheshark.com founder Jon Hein. This is a reference to the popular and enduring shows which have featured him in their declining years often to replace a departing regular castmember. Such shows include Happy Days, The Love Boat and Dynasty.Hein writes that this is not a comment "on Ted's fine acting skills" and that "he has a great sense of humor about it, too". In one episode of Married... with Children (a show that stayed on the air for six seasons after McGinley's addition to the cast) McGinley himself spoofed this fact by asking Al "Another picture, captain? I mean, Fonzie? ....Al?". A 2003 issue of People that focused on McGinley's casting on Hope and Faith was titled "Ted McGinley Is Not a Killer", referencing his reputation for causing shows to jump the shark, though his long involvement with Married... with Children may have had the opposite effect: As Jefferson D'Arcy, a charming scam artist, and Marcy D'Arcy's husband, McGinley's contributions may have enabled the series to have a longer and more successful run with many fans preferring him to his predecessor, played by David Garrison.

https://en.wikipedia.org/wiki/Ted_McGinley