I mean there’s no way to determine this unless a writer writes a comic on this, but the symbiote does affect your personality.

Venom don’t affect the nature of the host. He will be still worthy. Even that was happened in what if series.

When a symbiote takes over a person it’ll not only affect body it’ll influence the host’s mind too because of it’s awareness or consciousness. The parasitic bond created between host and symbiote makes it easy. So when a symbiote is present that time he won’t be worthy. But there is a possibility of him being worthy as he’s a strong minded person because after losing everyone he loved he still fought for righteousness without losing his mental balance ( considering events before the decimation). If we consider events after decimation then mostly symbiote will influence him more than him influencing it. Hope this helps your curiosity. Thank you.

Thor won’t be worthy You can also see that in an episode of the cartoon series where a symbiote takes over Thor and he isn’t worthy anymore