I would have to say it was one of my early Brokers Tony Lewis . The man had no moral compass. His philosophy was "The Agent who sells the most is right" which of course led to the top two agents stealing clients within the firm. His lack of a moral compass showed up in many other ways as well. 

My worst experience in real estate was handling numerous short sales 2008-2012 and knowing the pain of those who were losing their houses.

The imploded septic tank during the septic inspection the week before closing. Yes, imploded and not exploded.

Why focus on the nightmares, let's keep our focus on the wins.

I drop in on a wave knowing it was a realtor i knew. He was on a stand up board and whack me on my back. Ok it didn't hurt, and it was in fun but what a jerk. I was surprise by his uptight response, what can't share? When my son and his friends found out he whack me, it didn't go well for him with the local crew. Ok , no big deal life of a realtor.

No nightmare stories at all.

This should be everyone's too i.e. the statute of limitations & waiting for it to expire. Closing escrow is one thing, getting sued for whatever reason potential over the next 4 years (CA) is another. E & O insurance salespeople preach (fear) this as a closing statement to have you sign on. 

Had a guy carrying a gun in a home I was doing a open house.

I have never encountered anything like this. My worst nightmare would be a letter from the NC Real Estate Commission.

No nightmares for me. Whatever comes my way, I deal with it like a true professional, 

I focus on all of the wonderful blessings in life and in real estate.  

Tony Lewis no nightmares, just two different Sellers in 2023 that I wanted to fire so bad. I could not because we were under contract a week to close. I did handle it professionally. But I never want to hear from either one of them.

Parents. 

As a loan officer, a loan was approved for a couple to purchase a one of a kind home on 5 acres. Four days before closing the survey disclosed a pipeline easement the ran under the house. Luckily the buyer was well heeled and his wife wanted that house. After an exeception was worked out with the title company, he paid cash. 

I went through a stalking situation that was an absolute nightmare.  Terrible experience. 

Not sure if I ever have had a "worst nightmare", but a few times new clients made the hair on my neck stand up.

We avoided the worst last year- but we set the closing based on a tenants lease ending. The tenant didn't want to leave. He ultimately did leave 5 weeks late- but had it gone to landlord tenant court, it could have dragged out for 1-2 years. 

As condo board President- I had to foreclose on my neighbor for defaulting on monthly common charges and special assessments. It took nearly 13 years from default to getting new neighbors in. 

Having both mothers show up for a home inspection! Long and painful, eliminated any chance of closing.