What is, in your opinion, the most dangerous jump and why?

I think I'd have to say any Warhammer Jump, the Lord of the Mysteries Jump, and any SCP Jump.

Warhammer because Chaos would certainly notice some powerful stranger appearing out of nowhere, and would definitely want to grab a hold of them, so you'd need multiple anti-corruption and manipulation perks to even set foot in any of them without risk. Once you get past that, Chaos is still going to be a massive pain in the ass, since again, you'd need multiple different perks in order to get a shot at the Chaos Gods, let alone kill them. And if you don't have those perks, the Chaos Gods will never stop trying to get their fingers in you.

Lord of the Mysteries, because simply by knowing about the Outer Gods without being a high-sequence beyonder means you'll get an instant, "Game Over" when you arrive in the jump. And even if you do, you'd still face the same risks as you do in the Warhammer Jumps. Not to mention, if you're not a beyonder of the Door Pathway, or if you don't have some good stealth perks, then you can't leave earth if you ever wanted to, because then you'd catch the Outer God's attention anyway. Which is the last thing anyone in that jump wants. Just take a look at what happened to Mr. Door.

Any SCP jump, because I'd need to get a perk that allows me to have countless hands in order to count the sheer amount of cosmic and conceptual horrors there are out there, case in point being the Scarlet King. And any jumper worth their salt would catch the attention of all of them simply by existing. Additionally, the SCP Canon is as malleable as playdough, so it's a roll of the dice as to what kind of cosmos you'll get when you pop in and trust me, it matters a lot.