How do you say are a big pain in french?

There isn't a direct equivalent to "are a big pain" in French. However, depending on the context and the desired level of formality, you can express the idea in various ways:

Informal:

* Être un vrai casse-pieds: This translates to "be a real pain in the neck."

* Être une vraie plaie: This translates to "be a real plague" or "be a real nuisance."

* Être lourd: This translates to "be heavy" and means "to be a burden" or "to be annoying."

* Être chiant: This is a very informal and vulgar expression meaning "to be annoying" or "to be a pain in the neck."

Formal:

* Être très pénible: This translates to "be very troublesome."

* Être très difficile à vivre avec: This translates to "be very difficult to live with."

For a more specific context, you could use phrases like:

* Tu me donnes du fil à retordre: This translates to "You are giving me a hard time."

* Tu me rends la vie impossible: This translates to "You are making my life impossible."

The best way to express the idea of "being a pain" in French will depend on the situation and the relationship between the speakers.