On the behalf of story perspective related to Venom, it's described that it is an alien which can't outlive in atmosphere of earth without companion.
So, eventually Venom always searches for a person who's in search of power or influenced by it or even finds leverage. It takes control over that person and bounds with it. If it's successfully connected to that person meaning that now both can leverage upon each other.
In such a way, Venom offers Tom Hardy cure to his cancer and also a support from him to live in his body for survival of it's own. So it's like Tom is the driver and venom itself is a car.
So what you can consider venom is that it's a vigilante which is under influence of it's host.
If host is willing to act good guy meaning that Venom will also drive thought that scenario (In this movie), and if it's hosted by some bad or evil guys it'll be evil. (Why? Because they're psychologically connected !)
*See the Spiderman 3 for such reference when Eddie connected to symbiote feeling hatrated towards Spiderman and venom beacoms villan.
So Venom is neutral in such behaviour and totally depends upon
it's host carrying it. It just finds leverage or weakness of host to
make deal with.