Myth Hercules did took upon his shoulders the heavens/skies (from Atlas), which I believe would be his greatest feat of strength in the tale.
But, Fate Herc would had done the same.
Overall, the OG Myth is just too mild in comparison, I believe. Even if you somehow equiparate Greek mythos to Nasuverse, in Nasuverse Hercules HS/Servant would have the NPs, God Hand and Nine Lives, both which would be upgrades to the original power of Herc.
While OG Herc had to cut -> burn each head one by one, for example, Nasu Herc developed his technique to the point he could "simultaneously annihilated 100 heads with a bow."
Servant Berserker Heracles would be physically weaker than Myth Heracles, but would probably still win in a fight because of speed/reaction/etc.