As the comments about "at the height of Time Lord power" might hint, *when* you pick for your universe can certainly matter. Choose wisely

The Book from Lot… wherever… would, IMO, defeat many contenders, but suffers from several problems:

Someone with a more consistent definition of "infinite" than mine would probably say that it should be banned.

---or---

Its source universe is finite, and it only affects a finite area (leading to the hilarious fight where it gets chucked into, say, the Star Wars universe, but only affects *our* galaxy - and its side doesn't even consider the possibility of this type of failure, and are baffled at the opposing universe's "immunity").

Also, it's kinda a one-shot - if the trick fails, it's unlikely to succeed on subsequent attempts; if it succeeds, it cannot really be recovered to be used again (important against infinite-sized universes, and multiple engagements).

And, hilariously, if the other side jumps entirely into the Book source universe, it could technically fully work, yet ultimately cause zero casualties.

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Reading comprehension has never been my strong suit, but here's the factors I remember hearing that it sounds like people think would be important in determining who would likely win:

Time Travel
(Temporal defenses)

If the enemy can go back in time to destroy you before you know that you're fighting, or just break your universe's concept of time, are there any universes that can defend against this kind of attack without Time Travel of their own?

FTL Travel
(FTL attacks, attack while FTL, FTL defenses, FTL senses)

If your foe is moving and attacking at relativistic speeds, can you win if you are not?

WMD
(Divinations, defenses, size does matter)

If your foe is destroying things at the planetary scale, can you win if you are not? How many worlds does each side have, and how fast can they destroy them?

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Personally, I hope that the final answer isn't so boring as to obviously fall along such lines (plus things like universe size vs movement rates or range of senses / attack range).