Toxic Masculinity is a concept thrown around a lot by feminists and BPers, and varies widely in definition from "men not going to the doctor for fear of being ridiculed" or to encompassing any sort of masculinized behavior:

Toxic Masculinity refers to how The Patriarchy's gender roles are harmful towards males, "real men do X or Y" this has to do with traditional masculinity and traditional masculine gender roles.

Overall, simply striving to achieve a form of validation or admiration for some particular quality isn't toxic. Women putting on makeup or wearing clothes to make themselves look better isn't toxic. Achievements of any part of life have winners and losers. Not everyone will be able to viewed in the way they want to be viewed, just like not every man will be thought of as masculine. Guys wanting to workout to look more muscular or like a stud aren't harming themselves.

Secondly, there is no definite correlation between masculinity and inherent toxicity or harm to oneself. Many men benefit greatly from masculinity in excess. In a physiological sense, Barry Bonds and his steroid usage got him fame, an amazing career, and several MLB home run records.

Lastly, boys with no real masculinity at all (or attempt to be viewed as real men) have complete and utter toxicity that destroyed their lives.

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

In the murder of James Bulger, two 10 year old boys brutally tortured and murdered a 2 year old baby.

As a whole, my view is toxic masculinity doesn't exist, as no amount of masculinity or the desire to achieve masculinity is toxic.