In the comics, superpowered individuals can take decades to go from good guy to bad and back again: on the big screen there is a lot less time to show audiences quite why the chap you just saw helping to save the known universe has just decided it might be a good idea to destroy it.
There’s a reason Tom Hardy’s Venom has not yet battled Spider-Man in the Sony-owned Marvel movies, beyond the tangled web of contractual ownership of Tom Holland’s masked wall crawler.
