Tel-Kar is canonically the first host of the Venom symbiote - however, this is mostly overlooked because Tel-Kar is an alien, meaning that the title of 'first human host' can still go to Deadpool.
Venom bonded with Tel-Kar after the Kree race decided to weaponise the creature, using it in the war against the Skrull, where it would act as a spy for the Kree forces. However, this first bond saw itself be cut short when the pair were caught in a ship crash, with Venom having its memories of the host wiped.
The first host would hunt Venom's offspring down, trying to bond to the newly created Sleeper. Proving that this was perhaps not his best option, the symbiote would lobotomise Kar, using his body as a host while he explored the galaxy - proving that Venom could be significantly worse to its hosts than it is.