The Superhero Database Classification number, or SHDB Class, is a number that represents the overall 'power' of a character. All traits of a character are used for calculating the Classification.
What it DOESN'T mean
This doesn't mean that a higher class would always beat a lower class character. But the bigger the difference in Class is, the more obvious it is who'll win in a fight.
How is this calculated
( INT^1.3 + (STR*0.5 )^2 + (SPE*0.5)^2 + DUR^1.6 + (POW + (SPS*SPL))^2 + COM^1.8 ) ^ TIER
Super Power Score and Level
Every Super Power has a score (SPS) that is used to calculate the Class. Each Super Power also has 3 levels (SPL). The level is set when connecting that Super Power to a character. The level determines the final score, of the Super Power, being used in the calculation.
with 100% certainty.
Here you can see Gun Jack being struck by nuke from orbit - and he simply tanks it.
And of course if you spam Blonde Bomb with Nina you can easily beat Gun Jack, he cannot even stand up from ground once he's down if you do Blonde Bomb because he's so thick and the move still hits him.
So yes.
Nina can harm (and also beat) a nuke-tanking opponent (e.g. Gun Jack).