Thoth had the more impressive scale feat. Through sheer will, his power was keeping literally his entire Universe alive and preventing entropic collapse and destruction. And IIRC he was doing it rather casually (But for some reason, Cosmics who operate on a Universal scale are above Skyfathers according to some).
Forsung on the other hand had the more impressive fight with Odin. Thoth would beat regular base Forsung but would probably lose to the one who fought Odin.