"My sister's husband is very unfriendly."

Translation: Le mari de ma sœur est très antipathique.

[Yves991549]

"Le mari de ma sœur" is "mon beau-frère ... think of it duo !

[geoffreymayer]

"Beau-frère" is "brother-in-law". That is good to know. The sentence to translate has "sister's husband", not "brother-in-law", so "beau-frère" is not a correct translation.

[Stephen774655]

Whats wrong with hostile?

[Yves991549]

hostile seems to be better than antipathique

[Yves991549]

the right translation of "antipathique" is "unsympathetic"

[speedy1]

Can't I use disagréable?

[edZGwD]

Ou désagreable?

[LeesaWheel]

Would the correct translation of the above sentence be: "My husband's sister is very unfriendly"?

[geoffreymayer]

No, it wouldn't. "Le mari de ma sœur" is "the husband of my sister", which is "my sister's husband". "My husband's sister" is "la sœur de mon mari".