Meliodas' ultimate power level has not been officially released by the author.
The last time Meliodas' power level was estimated, it reached a total of 142 000 (Volume 29). This was Assault Mode Meliodas, which is theoretically his original form and strength (as described by Merlin and other characters).
However, after his possession by the Demon King, ...
We cannot be sure.
The first reason is Britannia's size. While Britannia and its surrounding areas might be based on the real-world United Kingdom, the story considers it as a continent, not a country. This would mean that there is a possibility of Britannia being bigger than its real-world counterpart.
Another reason is that as far as I know, only ...
Merlin is a human from Belialuin.
Belialuin was described as the "capital of the wizards" 3000 years before the events of Seven Deadly Sins. Although Merlin's true name has been shown to use an inhuman pronunciation and alphabet, the latest chapter (Chapter 337) showed her childhood extensively, detailing her motivations and origins.
Unless these facts ...
Okay, so basically thanks to fellow Redditors, that sounds like a little plothole. The main reasons expressed there are:
It is not an immunity, it is an ability to nullify Commandments.
She forgot that she had this protection on her (the blessing happened 3000 years prior to the main story), which explains why she still suffered the effect.
As for "Is it a ...
As far as we know, Mael does not possess "The One", but does not have a weaker form at night either. It must be noted that Ludociel refers to this Grace as Sun (「太たい陽よう Taiyō」), and not Sunshine, which may imply there is a difference between Escanor and Mael's use of this power.
A popular fan theory is that Escanor possesses an unnamed innate magical power ...
As read on the wiki article on commandments
Anyone who shows their back to the wielder will become an obedient slave of the Demon King and by extension, his representative and youngest son, Zeldris.
As per the wiki's page on Balor's Magical Eye, the highest known-for-certain power level recorded in Nanatsu no Taizai is Ludociel's impressive 201 000 (Chapter 286, page 14). However, we know that Mael has a 200 000+ power level (Chapter 278, page 12). As this is relatively vague, Mael may or may not have a numerically higher power level than Ludociel.