Hi Reddit,
There is a TON of backstory for this, but I'll try to be brief. My wife (33F) and I have been dating for more than a decade, friends since we were 14, married 1 year (I know, we took a long time, but school/work/family always came before a wedding.) This means I have been in her life (and her families' lives) for years. Her family and mine could NOT be more different, but I wouldn't change that for the world. Most of them are amazing people who genuinely care far too much and are more than willing to give you the the shirt off of their back if it means they can help you.

My wife is everything that makes her family amazing, but with so much more (yes, I am bias.) She has 2 older sisters, one of whom I'll call Megan (36f) who I have had the pleasure of seeing grow from a into a wonderful woman, mother, and professional who I love being around. The other sister (41f), who I will call Karen... has never had that transformation.

Over the years this woman has been a menace. I feel she is a classic narcissist, constantly turning family members against each other and twisting stories to suit her narrative. For reference, when Megan was having marital strive, Karen took it on herself to "investigate." She alerted everyone Megan knew, told friends and family she was having "a mental breakdown" and even went to Megan's boss (she works in a field where this put her on a PIP) to "make sure she got help."

She sided with Megan's ex, and turned much of their extended family against her - until the divorce was finalised and the family slowly pretended they hadn't basked in Karen's meddling. When Karen later got divorced herself, she forbade the same family members from speaking to her husband, only letting her narrative be heard. She demands extravagant presents and trips, and when my wife refused to go on Karen's "divorce vacation" because it landed 1 month before our wedding and would cost $5000, their mother's veil, intended for my wife, which Karen was entrusted with, "magically" went missing. This is too much unrelated information, but I feel its necessary because Karen is... a real piece of work.

On to the juicy part. When my wife and I were in our early 20's, she had some serious mental health issues - all food related. We had just moved to a new city, in a new region, and she was at the lowest point of her life. Through amazing self discovery and years of hard work, she beat her eating disorder - but not before her sister's tore her a new one. Karen constantly ridiculed her weight, mocking her for being "too skinny" even when my wife was trying so hard to get better. On the heavier flip side, I have always been a bit chunky. My family are straight shootin' Texans and we have a bone structure and thorny disposition to match. I'm not defending my family's ability to be mean, but it means that we are predisposed to conflict-something her family avoids.

Over the years, she has made SO MANY COMMENTS about her sister's weight, my weight, and random ass stranger's weight that it's almost funny. Except, there is nothing funny about listening to a 40-some-year-old sh*t on people's weight. Karen herself has ALSO struggled with her weight, but mostly due to her nutritional/fitness goals. She has worked on muscle bulking for years, changing her diet to maximise gains- and after 5 years of maxing on protein, she's got some impressive guns. But also some extra beefiness that any nutritional expert might have told her would happen on that diet.

Whelp, after more than a decade of Karen's b**chy nonsense, she's started taking ozempic. A family event is coming up for a family member that Karen has open trashed talked for decades (despite him being literally 20 years her junior), and unsurprisingly after 30 years of instigating, everyone is over her BS. The age of the internet and my wife's dedication to watering her social garden has all but killed Karen's ability to stir the pot.

Here is where I will be the a-hole. Karen is coming to this event to show off her Ozempic body. I want to be clear here: I have no problem with people using this drug. I only have a problem with Karen and her decades of body shaming BS. I want to make sure she feels the exact same way about her Ozempic gains as each of her sisters, her countless friends, and the random stragglers she has ever taken shots at.

So, Reddit, am I the a-hole for wanting to sling insults at this woman for using drugs to win a battle she has ridiculed countless others for losing?

To add: I read this to my wife and she is on board. I am more than willing to take on this battle and she already has 1.5 feet out the door of this relationship.

Update:
The travel surrounding the event has become a whole thing. A simple graduation has turned into the "Karen show." After she recommended a $700+ per room PER NIGHT Air BnB, the younger cousin cancelled his party. He avoided the drama by being bigger than all of us and giving up his big moment. No one knows how he figured it out the drama around it, or made his decision, but so many of us are so very proud of him for his maturity and so very disappointed that he, yet again, has to dull his shine for her ego.

Thank you so much for your input, some of you had some truly spectacular advice.