Being broken into pieces via freezing should be checked by durability— unless you wanna try freezing a diamond until absolute zero. Sure, she could freeze him, but no guarantee if she can hold him for long with fire moves AND higher AP.
Just because Time Stop and Ice works doesn't mean she insta-wins. Amphy surviving a round of that is likely, and him making himself more resistant to her offense and himself stronger for some attacks. Even without the boosts, Amphy's taking only a third of what would normally put him on his ass from an ice type of his exact strength. Adding boosts on that almost erases her advantage with typing, and boosting his offense makes her defenses even smaller. Unless Esdeath has knowledge of all of this and kills it ASAP, even if Amphy is staking up towards the later half of the fight, he reduces her damage to nothing and wins.
Let me re-explain why:
Ampharos is Thicc (compared to Mons on his level). Mega Ampharos is extra Thicc (again, by comparison).
Things that boost his defenses; Cotton Guard (drastically, "physically" if we even need a distinction between having the durability to take solid, tangible shards of ice against the body with the physical stat, and the more "mental" special defense stat), Light Screen (special defense, so if we ignore that difference, it's just more durability), and Magnetic Flux (for both types of defenses, with his Plus ability).
Ampharos' Durability scales to his AP, being comparable to other versions of itself and Mons of equal level. All of this makes her 1/3 damage to that durability (which was boosted) far weaker.
Then, we have him Growling at her to "lower her attack" however that works. So if we treat it like Ice Shard, making the move "Physical", then it's almost worthless. Most shit that isn't an energy beam or a mental attack should be physical imo, but let's not bother with that.
We have Cotton Spore lowering her speed— that brightness distracting her, a fire punch that might not be boosted but with the AP gap it's definitely more likely to break than if it was equal to her Ice Walls. Fairly certain that the significant AP difference weakens that fire resistance, unless she's had shields that took stronger fire damage.
And omnidirectional discharge that probably would shatter that same Ice with a good Charge— which makes his defenses increase further AND blasts her shields with a 60+++ GT blast of electricity that she HAS to take with a shield or her body.
Yeah. Esdeath loses.