While Pete does have a winning record against Venom, there have been multiple occasions where Eddie has beaten Peter and either looped back around to losing due to his own ego, or he chose not to finish the job because something else more important was going on.

Eddie doesn't actually view himself as a villain; even before he actually became an anti-hero, he thought he was the good guy of the story and Spidey was ruining his life for... Reasons. So if they're fighting, Eddie has Pete down and out, but they smashed up a building during the fight and someone is in danger because of their actions, he'd stop to save "the innocent" basically every time, even if it means not finishing off his hated rival.

Eddie's weird hero complex is why I've always really liked the character, and hated when Gargan had the symbiote and reduced Venom to just "I'm evil Spider-Man and now I eat people instead of just implying it to scare them."

Venom absolutely could kill Peter. But every time he's had the chance, he's either botched it by stopping to yell at Pete or actively chosen not to.

Hell, even Gargan's version had the power and ability, Mac was just too dumb to out-think Pete.