The primary reason I'm still cautious about giving an outright Continental rating is that we still don't know how Mizari would perform the feat.
Going further as a devil's advocate (to my own post no less lol), it was never specifically stated that she would destroy the literal Ingracian continent or just the capital/kingdom.
We also obviously can't scale the WN from the LN, although I suppose it's context for being the original/rought draft nonetheless.
Mizari was more terrifying than some demon lords. She wouldn’t break a sweat in destroying the Ingracia Kingdom.
[Volume 11, Chapter 4]
Although I'm still inclined towards the former, as "Kingdom" here repeatedly refers to its borders, insinuating that "Kingdom" spans the entire small continent.
Anyways, I'm just asking people's opinions about this regardless.
There are likely better scaling feats in the Empire arc, especially whenever Carrera is in action, but those are from MTLs which can really get confusing.
As for Charybdis's speed, I honestly am unsure. The Megalodons were also described to be difficult to dodge, but it was due to its size and, since it likely refers to mid to close range combat, refers more to the Tempest people's slow travel speed. Charybdis never actually dodges (or tries to) AFAIK, although Veldora lists "body slam" as one of its attacks in his journals and it does try to attack Treyni by ramming itself against them, so I dunno, I'm all ears.
Their attack speed would be Massively Hypersonic+, probably. Since Tempest Scales were described to be difficult to dodge, albeit it also has something to do with the amount (tens of thousands). I am unsure if its Light Beams would be considered light beams since it was never stated as such, but has always been described as beams of light opposed to just energy beams.
The reason I'm once again cautious about giving it an Island level durability is because monsters below that level are capable of damaging Charybdis. Even Treyni, who is only Mountain Level+ in her first key (she was able to damage Laplace however who has Large Mountain level dura though?), was described to be able to deal damage even with her strongest attack being reduced to 1/10th of its power. Just that Charybdis instantly regenerates it anyways.
According to Treyni, even Aerial Blade—the strongest elemental magic spell she had at her disposal—was reduced to only about a tenth of its natural power. Far from the deciding blow it was meant to be. It did deal some damage, but as she put it, the wounds immediately healed themselves.
The only justification I can think of for this is surface area stuff, like how a mosquito can pierce our skin, similar but of a different scale.