8. Literally Sucked The Life Out Of Him (Twice)
Let’s stick with the multiverse theme for a moment.
While a competent host certainly makes things easier, the Venom symbiote itself has proven that it is perfectly capable to destroying Spidey on its own.
This is evidenced by the events of What If? #4, titled “What If the Alien Costume Had Possessed Spider-Man?”. As it turns out, the answer to that question is “nothing good.”
In the Earth-1089 reality, Spidey waited too long to get the suit checked out by Reed Richards. In turn, the entity permanently bonded to Peter Parker and began to suck the very life out of him. Once Peter had nothing left to give, the Venom symbiote abandoned him, leaving him to die of old age.
Worse yet, that’s not the only time this has happened.
In What If? #114, we see the Earth-9811 reality, in which the Marvel heroes were forced to spend twenty-five years on Secret Wars’ Battleworld. During that time, the symbiote, once again, took over him. This time, however, instead of leaving Spidey as a decrepit old man, it stayed attached until Peter Parker was nothing but bones.