Goku had to summon energy to counter it, so I think it is stronger than Goku. By how much depends.
If you follow scaling from Freeza saga, we see SSJ Goku with Kamehameha match 100% Freeza with Nova Strike.
Kamehameha is at least 2.22x but let's round up to 2.25x.
150 million x 2.25 = 337.5 million
337.5 million/120 million(100% Freeza) = 2.8125
The Supernova is supposed to be Freeza's ultimate attack, so I would expect it to be at least as good as another of his attacks. I'm inclined to give it the same multiplier as Nova Strike if not more.
Cooler should at least be as good as Freeza at amplification, though I think he's faster at it(I think it was in the sub and dub both).
5th form Cooler tanks a Kaio-Ken x20 Kamehameha and is later tanked by SSJ Goku. This gives a tank gap substantially less than 2x to fit in here, as Cooler would have to be largely ahead of 20x base Goku and largely behind 50x base Goku. A range of 1.5-1.6x works for me as it is in the median range.
Considering that, if Cooler's Supernova was 2.8125x his 5th form power, that ends up being around 1.7-1.9x SSJ Goku's power(rounded up).
From there it depends on if you think Goku would be able to at least remain intact long enough to summon a kamehameha to counter that power.
