I don't like the smell of mince when it is first cooking.
However, perhaps "vomit" is a smell I cannot stand.
I'm sure there are some more but cannot think of any, and will probably remember some when I see other answers.
I don't like the smell of poo, but being a nurse there are few smells that I really can't stand. You kind of get used to all the different bodily smells over time and become immune to it all. Hardly notice it after a while.