According to Guinness World Records, which two spider groups are the main contenders for the title of world's most venomous spider?

Atracidae funnel-web spiders and Phoneutria wandering spiders

Guinness World Records identifies two main contenders rather than one uncontested species: funnel-web spiders in the family Atracidae and wandering spiders in the genus Phoneutria. Rankings vary because 'most venomous' can depend on venom toxicity, dose, and the organism used in testing.