Ja'ba Fofi (Giant Spider)
I've kept tarantulas and scorpions as pets, including the largest scorpion species and the most poisonous scorpion species. I think arachnids are impressive predators(I love seeing them hunt) and that they look cool. If I was to see a giant spider I would not be sticking around to check it out, spiders don't attack unless they feel threatened. If I surprise a giant spider and it attacks I'm sure I'd be able to kill it, but it would be a harrowing experience. Also, the larger the arachnid the less dependent it is on it's poison to capture prey. The most poisonous spiders and scorpions are among the smallest. So I don't think a giant spider would have extremely poisonous venom, just lots of weak venom.
"You cannot rule out the possibility that an extraterrestrial civilization perhaps a million years more advanced than ours has the capability of reaching the planet Earth." ~ Dr. Michio Kaku