I had a serious case of chickenpox right before I turned 21. All over crust, mouth, eyelids, ears, groin.....I smelled like I was rotting and eventually was hospitalized for two weeks. The nurses took turns or drew straws or something. I pretty much went out of my mind for awhile.

On a positive note, afterwards, I didn't have any kind of acne for like 5 years.

A client that apparently didn't took a bath for a long long time. The person's smelled like piss, sweat and dirt. It was horrible. I don't know how I survived the encounter because the person wanted to talk forever. God bless I'm far away from that position now.

Liposuction fat

A mixture of fart and sulfur. It was so bad I could puke!

Vegemite

Ammonia. It doesn't technically smell bad, but it stings and does horrible stuff to you. Had the misfortune to use a lot in Chemistry and ended up puking from poisoning.

That and diarrhea and diarrhea farts.

Coffee ground emesis, and stool from a patient dying from a GI bleed. Absolute worst smell I have encountered in my life. It's also a smell that sticks to you.

Ammonia

Many years ago, I went to a plant manufacturing cooking oil. We were installing new fatty acid deodorizers. Damn, they needed them.

Pulp and paper plants are pretty nasty; and food processing plants with wet/rotting grains are vile. I used to get highly amused by auditors puking. Raw sewage generally smells better - lol.