"I wish you were my big toe so I could bang you on every piece of furniture in my house …" the 23-year-old wrote.
It didn't take long for the internet to turn on him, slamming the star for "degrading" his girlfriend with his crude remark.
"This is honestly disgusting and I feel so sorry for this girl," one person pointed out.
"Sad how you brag this woman as an object. Sadder how she doesn't know her value," another said.
Someone else slammed the comment as a "creepy caption".
"Simply degrading picture with a degrading caption," another fumed.
Others called him out for sharing such a personal photo, one that should probably be locked away in a private vault.
"Dude, how can you show your girl to the world like this?" one asked.
"This is waaaaay to much," another said.
One said: "What is the next step, doing porn?"
Some called on Alvarrez to "recognise" his role as an influencer and think twice about sharing such content.
"Recognise yourself as an influencer and understand the responsibility that you have," a follower ranted.
"Wonder what her parents would think of this?" another mused.
However, it appears Fradegrada is a fan of the extremely racy shot, commenting with a string of emojis including a laughing face, a devil and a heart.
A quick scroll through her Instagram feed shows she's no stranger to sharing nude photos and images of herself in skimpy swimmers.
It's not known how long Alvarrez has been dating Fradegrada, who is best known as the creator of the "upside down" bikini.
Alvarrez, however, is most well-known for his public breakup with Instagram model Alexis Ren who, during a cryptic rant about their breakup, accused her former lover of having a "small dick". Ouch!
