"What happens if you give every horrible trait and disease to a Crusader Kings 3 character?" is a question I had never thought to ask: but as ever on the internet, someone did ask that question, and now we have an answer.
As you've clicked on this article, dear reader, I suspect you might have some idea of the horrors you are about to witness - but be warned, this is proper nightmare fuel.
Reddit user "i_hate_usernames" took it upon themselves to enlighten us all by applying every single disease and ugly trait Crusader Kings 3 had to offer to their character, King Svend II Ulfsen of Denmark. Bubonic plague, typhus, smallpox, pneumonia - this guy has them all, and he's even been made a toadish scaly drunkard to boot. "This is you, unfortunately" indeed.
As diseases and ugly traits come with various stat penalties, poor Svend scores zero in absolutely everything apart from stewardship, so at least he still has a promising career ahead of him as a banker. Although I'm pretty sure if you unpaused the game, he would simply melt into a steaming pile of goo.
I used the console to add every disease and ugly traits to my character. Here is what he looks like (NSFL) from r/CrusaderKings
While this feat is basically impossible to achieve by playing the game normally, i_hate_usernames managed to create this wonder through the game's console commands, which can let you add or remove various traits and diseases. I suppose if you wanted to do a Halloween-themed run, you could do worse than turning all your characters into fleshy zombies.