How do you get to 10 megatons Octillion?
A supernova has about 1X10 ^ 44 Joule
(2.8 x 10 ^ 28)
= 10 ^ 27 MT
= 4X10 ^ 42 Joule
= 10 ^ 48 MT
= 4X10 ^ 63 Joule
And as for the starburst. The energy spread first so evenly.
Superman is so taken only by a part of the energy.
Where his advantage here is still that the energy of a Yellow Sun is coming.