Could Superman, Sentry, Captain Marvel, Bizarro, WWH Hulk (He can fly), Juggernaut (Flight also), Thor with OF, Doomsday (Flight too), Black Adam, Nova, Darkseid, Thanos, and Despero take out Galactus? No Prep.
Thanos had allied himself with Annihilus out of curiosity. When he learns Annihilus' plan is to extinguish all life in the universe, Thanos plans to betray him by releasing Galactus. Just before he can do so, Drax appears and kills him. Drax and Moondragon then release the Silver Surfer, who in turn releases Galactus.
Galactus proceeds to unleash a massive, omnidirectional blast that later becomes known as the "Galactus event." Silver Surfer is sent ahead of the blast by Galactus to herald the imminent destruction, as the unleashed "Galactus obliteration perimeter" wipes out the majority of the Annihilation Wave, more than three star systems and even vaporizes a Watcher.
So says wiki.