It really depends how much power Freeza was outputting, given it being far below his Namek 100% is still pretty vague when all 70% of his power accomplished against someone in the same league as his 100% self was some light superficial damage. The Daizenshuu describes him as "somewhat inferior to Freeza" which is also quite vague when it comes to the gap between them. Freeza also brings up the idea of them taking on Goku 2 on 1 despite believing that he can defeat Galu alone, which would seem fairly pointless to bring up if Cold were oneshot material to SSJ Goku as just bringing in an extra body wouldn't really shift the scales if they exit as soon as they enter the battle.
Comparing him to Namek Freeza's percentage, I'd say he'd be a fair bit above 50%, but likely still below 70%. I'd personally have him as equal to 62.5% of Freeza's full power.