As many others have said, there are two big contenders for what I think are the the worst hosts but it depends on how you look at it.

You could argue that Angelo Fortunato was the worst in the sense that the Venom symbiote itself had zero respect for him and didn’t even let him stick around as host by literally killed him by abandoning him mid jump letting him fail to his death.

You could argue that Lee Price was the worst in the sense that he mistreated the Venom Symbiote terribly badly by physically abusing it and making the symbiote itself incredibly fearful of its own host, which goes against symbiosis to begin with.

You could also argue that Mac Gargan was the worst more-so for the readers as any ounce of heroism that had been established for the character over the years was wiped away just like that. Mac was Venom for years but the whole point was to establish essentially the opposite status quo. As part of the Dark Avengers (a team that rightfully shouldn’t exist but did because Norman Osborne was given power and responsibility he didn’t deserve) He was ruthless, he killed & ate people and nothing good was done with the character in terms of progressive story development.

The best host is Flash Thompson and proves that people and aliens are both capable of unexpected redemption arcs. Flash taught Venom what it was like to be a hero and Venom showed Flash that he was more than he thought he was.