Guy I used to work with when I was security. Not the brightest guy in the world, but he was an army ranger gone reservist, got pulled back in, fought in gulf war 1 and 2, I have seen him empty a beretta92 into a 4" group at 20 yards and saw him once get attacked hand to hand by 5 guys, in the time it took me to cover the 50 yards to get there to help 3 of them were down.
I knew an undercover cop once. He was posing as a biker when I met him. Very scary. Big, strong, shaved head, tattoos. He played his part a little too well.
Care to divulge?
My best friend growing up is a well known criminal in Dublin. Absolutely, 100 percent not someone you want to cross for any reason.
My husband. He has a disability so he doesn’t scare me physically but he has a terrible temper and it’s impossible to know what might set him off.
Along these lines, the Gramps from Hell (my maternal grandfather) didn’t believe in threatening people; he was a complete charmer but, if he got mad at you or you simply happened to be around when he was mad at anything, you learned it when you saw the pointy bit of metal sticking out of your chest. He’s been known to make or destroy people’s second jobs as soccer refs, and I wouldn’t be surprised to find out he did it to colleagues in first jobs.
He led to the only time I can remember feeling psychologically threatened and actually getting scared rather than angry: when I tried to ask her for help against him, my mother’s response was “if your father hears a word of this, you won’t be setting a foot in my house ever again.” Ooooook, Mom, wuvya too.
I still haven’t been able to go dance that sardana at Barcelona’s Cathedral Square to celebrate his death, but expect to do it in the next few weeks. And I do take care of my mother, as expected socially in Spain (although sharing it with my brothers more than most people would expect), but it’s mostly because I don’t want to put my brothers in a “she or me” bind.
I’ve felt physically threatened by a dude I knew in Miami who was on disability due to some never-explained psychological problem and who had the hots for me. When I refused to drop my then-bf for him, he cornered me; once he saw he’d made his point, he left.
Possibly, if enough people are interested.
I’m another one to say my Dad - not just because he was a Bad Man, but because he has this kinda bad guy charisma (which explains why he got all his wives). Even when I went to visit him in hospital, he had it.
Some of the local bad kids have told my daughter that I’m scary. She thinks this is awesome, btw, and apparently it’s scaring them away from her. I’ve heard this quite a few times - and I’m not old old, crazy-bag-lady scary; I look like a nice middle-class woman and the likelihood of me actually beating someone up in anger is close to zero. I think I’ve inherited some of my Dad’s bad-boy charisma genes.
One of the other scariest people I’ve known (apart from my Dad) had hardly any teeth, beat people up at random in the park, always had knives to hand, and used to buzz my door threatening to ‘bugger me straight.’ He loved watching his two sons beat up younger children.
He ended up with custody of his five-year-old nephew after his sister-in-law lost him due to drugs and prostitution.
Most of the other rather bad people I’ve actually known, as in having multiple conversations with, aren’t actually that scary, as in you wouldn’t feel scared just talking to them. Like, I taught a few teenage boys who had some serious violent crimes under their belt, were known to be in gangs, and assaulted other kids in front of me, but I always felt they had limits and they didn’t do it purely for sadistic fun.
I am interested in hearing about it too;)
Sure, of course we’re interested!
It’s been years since she’s done anything mean to me, but my Mom is still the scariest person I know. She had a hair-trigger temper, but you’d never know what could set her off - and she could be very violent, erratic and irrational. Even though she’s changed, apologized for the past, etc and I forgive her, the thought of making her mad still scares the crap out of me.
I’ve known quite a few career criminals and honestly never felt particularly afraid around any of them. They were just hardworking people who had jobs that happened to be illegal. In the former Yugoslavia, I met ethnic cleansers. Some of them were rather scary thinking back though at the time and in the circumstances seemed completely normal and even safe to be around. Currently, the scariest person I see on a regular basis is one of the clients of my uptown fortune-telling business a rabid want-to-breed whose already blown six-figures in fertility treatments and failed adoptions. I fully expect one day to be find out she’s kidnapped or killed someone.
I think the scariest thing about this thread is the number of responses stating that one’s own PARENT is the scariest person they know. 
None that I can think of. Maybe some random Iraqi that was shooting at me. But not really, never met them and they were lousy shots.
Obviously.
Definitely interested. Love serial killer stuff.
I’m interested! John Wayne Gacy? The Sharon Tate murder guy? Ted Bundy? (I think he’s dead) Scott Peterson? The BKT killer?
Argent Towers, don’t be coy. 
Scariest person I know ? Must have been an ex boss. Bosses boss. We heard later that, when he did his military duty as a young guy, he volunteered for training in “hostile questioning”. He was a sociopath, no doubt about it, but one perfectly adapted to climb the corporate ladder. He was completely cynical in passing down the corporate bullshit. He made more then one male co-worker cry during their annual job-evaluation.
One of my college professors comes to mind. He was definitely on the good guy side of the table, very smart and kind and friendly. If a drunk tried to pick a fight he’d deescalate if at all possible, and would probably even take a few hits before defending himself. (He was a trained martial artist, and it showed in the way he moved.)
But if he believed you presented a real threat to his family, they’d never find your body. He’d pray for your soul afterward, but I have no doubts that he’d kill without hesitation if he thought it was necessary. He had that kind of resolve. If I had to pick a bodyguard he’d be the first on my list.
As far as bad guys go, I’ve met a few people that I’m determined to avoid, but don’t have any real horror stories. They all gave off plenty of warning signals. Fortunately I have yet to run afoul of any real psychopaths.
I’m interested, too!