In the final fight scene of the Venom movie, Venom takes down the whole spaceship which was going to take off and then protects Eddie from the blast. How did Venom survive that blast?
If you want a more substantial answer, one can be found in the lore of the symbiotes. For that, you need to be familiar with the comics. The abridged version goes something like this: By the end of the film, the symbiote and Eddie had fully bonded; they had become a single organism. Although the explosion had incinerated most of the alien tissue, as long as Eddie survived, a small part of the symbiote survives (at a cellular level). With time, it would regenerate enough of it’s biomass to take form again.