With reference to the name of a very large dinosaur-like monster in the 1956 U.S. film Godzilla King of the Monsters!, the noun Godzilla designates:
– a large or strong example of its type;
– a person or thing of monstrous proportions or strength;
– a fierce or frightening person.

From Godzilla, the suffix -zilla is used to form humorous, usually temporary nouns which depict a person or thing as a particularly fearsome, relentless or overbearing example of its kind. The noun Bosszilla occurs, for example, in the following ‘boss card’ sold at The Infinite Mushroom, an Orlando gift shop—as reprinted in Top dog gets no biscuit as Boss Day goes begging, by Linda Shrieves, published in The Orlando Sentinel (Orlando, Florida, USA) of Friday 16^th October 1987:

UH OH! QUIET, EVERYONE! LOOK BUSY! HERE COMES…
BOSSZILLA
THE NERVE-MANGLING PSYCHODRAMA
OF A YELLING, SCREAMING, SCREECHING
MONSTER WHO WONDERS WHY PEOPLE AVOID HIM

Among the humorous nouns formed with the suffix –zilla, Bridezilla (also with lower case initial) designates a woman thought to have become intolerably obsessive or overbearing in planning the details of her wedding.

The earliest occurrences of the noun Bridezilla that I have found are as follows, in chronological order:

1-: From The Bride Did What?! Etiquette for the Wedding Impaired (Atlanta (Georgia): Longstreet Press, Inc., 1995), by Martha A. Woodham, advice columnist for Elegant Bride magazine:

Wedding consultants have a special name for brides who are difficult and obnoxious: BRIDEZILLA.

2-: From the review of the 1998 U.S. film Very Bad Things, starring Cameron Diaz as Laura—review by Renée Graham, published in The Boston Globe (Boston, Massachusetts, USA) of Wednesday 25^th November 1998:

Laura is one of those women who have spent their entire lives planning their weddings, and she jumps into the project with terrifying military precision. She is Bride-zilla, an unstoppable force of nature who will not allow anyone or anything to screw up her perfect day.

3-: From Modern Bride Magazine Unleashes Bridezilla, published in Writers Write on Monday 11^th January 1999:

Modern Bride, whose recent redesign gave the bridal category its biggest shakeup in years, is introducing the first original, regular comic strip in the history of bridal magazines. “Bridezilla”, created by Los Angeles writer Kenny Kates and illustrated by Charles Stubbs, makes her debut in Modern Bride’s February/March issue, on newsstands this week.
Loosely based on Kates’ own fiancee, “Bridezilla” chronicles one woman’s wedding-planning odyssey, her metamorphosis into “the beast called bride-to-be,” and the havoc it wreaks on the lives of everyone involved. A full-page, multi-panel installment of “Bridezilla” will run in every issue of the bimonthly, which is read by more women than any other bridal magazine.
Gigantic, gowned, and bejeweled, Bridezilla represents “the monster in all of us,” laughed Modern Bride editor-in-chief Stacy Morrison. “Engaged women today have to have a sense of humor about the ordeal that can be planning a wedding.”

This illustration for Kenny Kates’s Bridezilla, by Charles Stubbs, was published in The Sun (Baltimore, Maryland, USA) of Sunday 17^th January 1999:

Coined after Bridezilla, the noun Groomzilla (also with lower case initial) designates a man thought to have become intolerably obsessive or overbearing in planning the details of his wedding.

The earliest occurrence of the noun Groomzilla that I have found is from Wedding Industry Targets The Groom With a View, by Rachel Emma Silverman, published in The Wall Street Journal (New York City, New York, USA) of Wednesday 16^th April 2003—as reprinted in the Asheville Citizen-Times (Asheville, North Carolina, USA) of Sunday 20^th April 2003:

The meticulous, demanding bride-to-be who plans every wedding detail down to the napkin folds has become an American cliche, if not a cultural icon. There was even a recent Fox TV special called “Bridezillas” that pitched itself as a view of the transformation “from blushing brides-to-be” to “matrimonial monsters.” But lately these marriage mavens are being usurped by their better half: the Groomzilla, a man who takes an intense interest in the minutia of wedding planning.