Formal:
* Je déteste les araignées. (I hate spiders.) This is the most literal and straightforward translation.
Informal:
* J'ai horreur des araignées. (I loathe spiders.) This conveys a stronger feeling of disgust.
* Je ne supporte pas les araignées. (I can't stand spiders.) This emphasizes your intolerance for spiders.
* Les araignées, je les déteste ! (Spiders, I hate them!) This is a more emphatic and informal way to express your hatred.
Slang:
* J'ai la phobie des araignées. (I have a phobia of spiders.) This is a common way to express a strong fear or aversion to spiders.
The best way to say it depends on the context and your personal preference.