All his neighbours are aware of his acrimonious nature.

Answer: Option C

Acrimonious : (typically of speech or discussion) angry and bitter.
Informal : having a relaxed, friendly, or unofficial style, manner, or nature.
Sympathetic : feeling, showing, or expressing sympathy.
Cooperative : involving mutual assistance in working towards a common goal.
Charitable : relating to the assistance of those in need.

Antonym of Acrimonious is Cooperative