Three come to mind, not sure which is scarier:

1. Road tripping as a youth during summer, saving money by sleeping outside as often as possible. Staying in a beach town, sleeping near the beach in a grassy kinda public area. In the middle of the night I wake up to some voices of aggressive sounding men talking about "fucking these kids up etc". They start hitting my friend or something else physical (it was only two of us), and in the moment, as I'm still literally waking up having not even opened my eyes, I realise this shit is real. My reflex was to get up to my knees and yell at the men "Fuck off Motherfucker". On my knees, feet still in the sleeping bag, being the skinny kid I was/am, I realise that some chunky looking bikie is in front of me and pretty keen to get violent and that I'm in pretty bad trouble. I was genuinely scared for my life then.
   • The ending to that one is that there were two bikies, and the second was actually behind me somehow. He kicked me in the head, I fell to the floor unconscious for half a minute and they apparently just walked away having got their fill of violence and luckily not too keen on anything extreme.
2. This one kinda doesn't count, but it felt scary at the time, also Content warning tragic loss of life involved ... driving late at night in the suburbs, waiting at the lights to turn into a major street, I hear loud and strange sounds I'd never heard before. My brain's best guess is that they're gun shots (which I've never heard in real life before). Lights go green and I turn into the street looking around for the source of the sound. Ahead I see a car turned on its side, stuff all over the road, and some people lying on the road and scrambling on the side of the street. I'm thinking that this is a shootout or something and have no idea what to do.
   • Turns out it was actually worse, but not for me. It was a car accident which had resulted in the car spinning, which, if you don't know, is awful and bad things happened. What's worse is that it was a drunken joy ride by a bunch of teenagers packed into the car.
3. Young and enthusiastic motorcyclist on a ride with my motorcycle friends. We've picked a road that's the most challenging we've ever done. Up in the hills, nice and windy with cliffs on the sides. I occasionally get dizziness (it's a thing) and got it in the middle of this ride, but was determined to power through. It's getting harder to keep up with the road though, and I'm making mistakes and relying on my breaks in the middle of turns. very very dumb stuff for any new motocyclists ... I should have just pulled over and reassessed the ride. Before I know it, in the middle of a turn, my bike wobbles, slips out from underneath me and I'm sliding along the road. Luckily I've got all the right gear on. But you don't know what it's like to slide helplessly along the road at >60km/hr speed, especially in relatively wild mountainous terrain. I still have the image burnt into my brain of seeing the road flying by the front of my helmet at that speed, relying entirely on my leather jacket, boots, and of course helmet to protect me until I stop and hopefully don't go flying off the cliff.
   • Luckily I stopped just off of the road and was fine apart from a sprained finger. The motorbike was mostly fine too! My friend riding behind me, however, probably got more scared than I, turning around the corner to see my bike on the road and me lying still and facedown on the side.
   • Lesson: apart from taking of yourself and not pushing yourself ... always wear the gear ... all of the gear!