I'll raise your cyberman and say that everybody is in trouble when Ultron enters the arena.
If we're talking Cyber Wars-era cybermen under the control of the Cyberiad, or late War/post-War cybermen with the Cyberium, Ultron wouldn't even be a speedbump -- the various human empires, including one that spanned multiple galaxies, threw shit like Ultron at the cybermen all the time at the height of the Cyber Wars.
They typically only worked once before they adapted and became immune (leading to the "upgrade. in. progress" meme).
Worse still, since Ultron is an artificial intelligence, albeit a partially Eldritch one, there's a good chance that the cybermen would just lobotomize and
subvert him -- yes, they are that disgustingly OP.
The only things
worse than the Cybermen at that stage in their history are the Daleks and the Time Lords at their own respective heights -- they were basically throwing reality-altering weapons at each other, doing all sorts of shit with weaponized timelines on a micro to macro scale...
anything you can think of, they used them and used them in amounts like party poppers at a continent-wide American 4th of July party.
Hell, the Daleks even had their own "Thanos Snap" in the form of a Reality Bomb, except that one only required a few planets, no Infinity Stones, and it crossed
all parallel dimensions and timelines.
Oh, and other reality-warping/dimension-hopping species on their levels got the fuck out of dodge when the Last Great Time War kicked off (the Eternals fled our reality screaming apparently, and given they were supposed to be energy beings like the Q but without the finger-snapping thing... yeah).
Doctor Who has some
horrifically OP things running around, haha.