I am sure I can make a calc out of this, seems pretty easy enough
It is an omnidirectional blast because the moons in the background say so.
The animation shows six moons, I will assume they are they the same mass as our moon
Feat Here: https://www.youtube.com/watch?v=krePiKLpVFI
Using Dont Talk's formula
.png){kind=link}
This is the feat
Moon Mass: 7.34x10^22 x 6 = 4.404x10^23
Earth Mass: 5.9X10^24
Add the two to get: 6.24x10^24
I will use radius of the moon in m to calculate frontal area.
pi * 1737000^2 = 9.4x10^9
So distance from the moon and earth is 384,000 km, so lets convert that to meters.
4 * pi * 384,000 x 10^ 3 = 4.8x10^9
And square that to get 2.32x10^19
The explosion has to cover 2.32x10^19
Lets be lazy and just times the gbe of the moon by six and use earth gbe
Moon GBE according to this wiki is 1.24x10^29 x 6 = 7.44x10^29
Earth GBE is 2.24x10^34
Add them up wont make a huge impact but it is one long decimal.
Just know I am putting this number in for my calculation in the long run
Explosion Size min /frontal area * gbe = answer
For the low end, lets assume only the moons were destroyed
(2.32x10^19/9.4x10^9) * 7.33x10^29 = 1.8x10^39
Dwarf Star Level
For those curious, this is about 4.4 times this feat
High end will use earth as a gbe for destruction
(2.32x10^19/ 9.4x10^ 9 ) * 2.24x10^ 34 = 5.52x10^43
Large Star Level
Scales to Necron and End Game Party.
This is necrons in game strongest attack, I propose High 4-C. We have High 5-A final fantasy already. Garland did that feat and he easily got killed by trance kuja... and necron is above him by a fair amount as well.
It looks as well that the explosion was condensed off screen via flash to white, but that is admitedly an assumption.
But math needs to be checked I think.
Edit: Also necron wanted to return everything to the Zero world, so destroy the world and everything around it, so using Grand Cross, it makes sense why the planet is the epicenter and why imo the high end is more accurate.