whats the cut off between 3-C(+) and 3-B?
The wiki generally denotes tiers based on explosions, so the size of the explosion is the important part.
As noted on the Attack Potency page, the size for a standard galaxy is the Milky Way.
Assuming you are creating an explosion of this size with one attack,
For a galaxy 2 million light years in size: 4*5.693e41 J*((4.75e+21 m/695510000 m)^2) = 1.0621397e+68 joules, or 1.0621397e+24 foe / 1.0621 YottaFoe, which is 3-C.
This was expected, since the distance between the Milky Way and the Andromeda galaxy is around 2.5 million light years.
The radius for an explosion that would destroy both of them would be around 1.35 million light years in size, just a bit larger than your example.
The next one depends on how far apart the galaxies are, and where the galaxies are relative to the explosion.
As long as the explosion that destroys them has a radius equivalent to or larger than 1.35 million light years, it will be Multi-Galaxy.
Anything less, and it will be Galaxy level.
And of course, if they were destroyed by separate explosions, the result would likely be even lower.
