A lot already mentioned, so those too, but also:

Rogue black holes. Just thinking about them makes my guts queasy.

If enough psychologists and civil servants wanted to, they could have you declared insane, and then nothing you say can come to your defense as you are now deemed too insane to be listened to. I know this isnt as straight forward as the average person thinks, but the possibility of it even happening once to someone is terrifying.

Oh that and trigeminal nueralgia, the worst pain possible forever.

My wife got a light headed dizziness this morning. The kids freaked out and ran downstairs trying to get me. As I approached the kitchen one of my kids, super scared points towards the kitchen area. I can’t see yet. My mind naturally goes… "She’s dead isn’t she? Oh yeah, she’s a gonner…WTF! Who’s gonna do the taxes? Who’s gonna feed the kids and get them to school? Who’s… I’m totally screwed! No! K love her and need her too much! Why is she just quitting on me like that! Bitch! WTF! Where is she!

Oh she’s fine! I finally make the turn into the kitchen. Its just another bout of high blood pressure. But I’m the crazy one for not eating all her ethnically correct lard cooked everything. Ooh! You gotta try the chocolate! Its traditional! Here, let me just add more lard and triple fry it for you…no way hose lady! She will just not listen. The good thing is she’s not that big in case I need to carry her around the house one day. I’m going to have to change her diapers and everything. That’s the scariest.

Snake clowns!

transmissible cancer, some surgeons had got cancers from thier patients by accidentally pricking themselves with a contaminiated instrument, although it was treatable and non issue once the tumor was removed. other forms like transplant patients is another source. rare t-cell cancers like mycosis fungoides, you go from patches, to “plaques” to tumors.

and there has only one case of animal to human cancer, the guy had AIDS and got tapeworm cancer from it, which is the most unusual situations out there.

Sometimes I think of the literal worst thing that could happen.

Like, going to hell, and being told you can leave if you complete some fucked up, borderline impossible task, like:

• Make friends with everyone else who is in hell. Not get them to like you. You must like them too, and enjoy their company. Yes, even Mother Teresa.
• Consecutively live through everyone’s life who has ever lived, as a passenger in their brain, you can’t control anything, but you experience all physical and emotional pain.
• Suck all sand until the earth is sandless. You have to suck each grain one at a time. Also, you have to find them, they’re not just in one big pile, also, there’s sand at the bottom of the Marianas trench
• Live your life on repeat until you live it perfectly. What does perfectly mean? You’re not told. Also, you’re not given any feedback after you die each time. If you try to cheat the system by having fun, you’ll be yanked back to hell and raped by demons before starting back at day 1.
• Achieve universal human genocide in 100 different times periods and starting points. Also every person you kill also ends up in hell, and know its your fault.
• Learn every vim function, then be forced to rewrite all the world’s code in nano.
• Translate every book, movie, song, and poem ever written into every other language, even dead languages.
• Think of a colour which doesn’t exist, then invent a new instrument, and play a song with a tune which has never been performed, invent a new language with a completely new structure, and convince everyone else in hell to adopt it as their primary language.
• read and reply to every comment on the internet. If someone replies, then you need to reply back. Every message must be unique and coherent. Also, spacetime warps to make it possible for everyone to be given a chance to reply to you.

Not having any feeling in your legs, but not being paraplegic, so you could legit accidentally walk outside without any pants on.

Abuse of the psych. bug that leads to faschism by smart evil people that know exactly what they are doing and somehow make it work stable for centuries.

Dying painfully

Some form of torture. The thing about torture is you can always add “and then…”

Psychological and physical

Imagine being forced to rip off your significant other’s fingernail.

And you might say “There’s no way I’d do that”

Sadly you will. Either to save yourself or them from more torture.

You will do it, we all would. That’s scary.

Nice try, sleep paralysis demon

alzheimers.

On the smaller scale it’s probably my wife and dog dying, in the larger scheme of things it’s the rise of fascism here in Germany and Europe.

Mondays

Prions - Actually nightmarish.