Anti-Moniter Vs Galactus

[Surtur]

AM would take it when he in his top form; when he was powered by his anti-matter universe.

What is his best feat in this form?

[Omegalith]

What is his best feat in this form?

Stalemating the Spectre in an Arm Wrestling contest that rebooted the Multiverse, pretty much.

[Surtur]

Stalemating the Spectre in an Arm Wrestling contest that rebooted the Multiverse, pretty much.

Was it through sheer power or through seeing the creation of the universe or some type of shenanigans like that?

[Eternal Torment]

Stalemating the Spectre in an Arm Wrestling contest that rebooted the Multiverse, pretty much.

Well, it was the Spectre when he was amped by the strongest sorcerors in DC at the time.

[Omegalith]

Was it through sheer power or through seeing the creation of the universe or some type of shenanigans like that?

Inexplicably, seeing the moment of the Universe's creation from within the Universe changes it dramatically.

So, when Krona saw a hand (Presumably that of the Presence, though it's never explained and no-one is there when A-M goes back to change it) through his time viewer, he broke the Universe into a Multiverse.

Basically, they made it so that Krona instead saw the interlocked hands of the Anti-Monitor and the Spectre, both struggling to be the only one visible.

[Eternal Torment]

Also, Spectre had to get juiced up to the point where he was screaming in pain just to stalemate Anti-Monitor.