Dark, i highly suggest looking him up. All i know is... hes an alien. Although he has taken Eddy's body (i'll say captive) Eddy Brock has no control over Venom (at first). Its an alter ego type thing. Venom uses Eddy's body to get back at Spider-Man... for whatever reason it is. I wanna say that Peter Parker knows how to stop the alien symbiote, and that may be a reason.
Reminder... Peter once had Venom attached to him... when he did that, he could enter Peter's mind and alter his thoughts... but not take over Peter.
Like i said look it up...
To be honest. I like this look for Venom. Its the classic look, but its not over the edge like the new comic Venom. They just keep making him bigger n bigger. It keeps the realism (even though he is an alien).
And maybe its the wrong thread... but i don't think we should expect him much in the film. I think that THIS scene will happen only at the end, and leave the audience DY'N to see the 4th movie... i think its a MAJOR way to make the fans begg. So, as a director, that would be my choice to do this film.