In my opinion, it goes:

1. Infinity Ultron

2. Kang the Conqueror

3. Scarlet Witch

4. Spot

Scarlett doesn’t want to hurt the multiverse, she just wants her family

The Spot also just wants to take vengeance on Miles. Neither of them have multiverse ending goals

Kang and Ultron are the top two and I’d say Ultron. Kang so far hasn’t shown as much feats as Ultron

Have you seen Miles’ visions, The Spot either killed some Spider-Men which I believe the consequences would be disastrous.

Have you guys wondered what happens when someone kills a Spider-Man from another universe?

There's literally no instance in Miles vision where any other spider men die. Just his dad

Well actully since infinity ultron killed thanos(which was the previous most powerful being in the universe) and he actually like killed everything in that one universe there’s no life anymore. He could actually hear the watcher. And the watcher exists in between space-time and reality, so he gained like another level of a consciousness, and was able to notice another plane of existence, and he has all the infinity stones and visions body, so he can easily just defeat, kang, scarlet witch, and the spot

1.Kang

2.The Spot

3.Infinity Ultron

4.Wanda.

Kang pretty obvious Spot he is higher than ultron becuase he can telports thorough the Multiverse Without The infitny stones and is breaking time and space even Knowing that not caring. Why is Wanda Low she could kill all of these guys but she dosen’t want to Do anything bad to The Multiverse and just wants her kids back.

So obviously Infinity Ultron is the biggest threat, but he's also the LEAST interesting in my opinion... aside from Wanda, we don't stan character assassination in this household

Overlord 427. Actually there is, in if you pause the scene at the right time it shows a vision of multiple dead Spider People (if you don't believe me, I was watching a YT Shorts video for it and it's actually there)

Meant to vote for Infinity Ultron.

Out of the these four I’d say Kang due to him having conquered multiple centuries. The guy’s got a trophy room heirlooms from killing heroes. Honorable mention should go to Dr. Doom. Or rather God Emperor Doom.