His amiable disposition suddenly turned diabolically sour.
I think you mean "amiable," a word that means friendly or good-natured. He had such an amiable personality that everyone enjoyed being with him.
The name Amy comes from the word amiable which means friendly.
agreeable, Friendly, likable, cordial, sociable
This made us amiable in the sight of God.
Amiable.
Amiable
aimable
The root of "amiable" is the Latin word "amabilis," which means "lovable" or "friendly."
Stacy's amiable personality made it easy to get along with her. Jolie was a very amiable girl and we became friends quickly. Most of the townspeople were amiable toward the visiting tourists.
Amiable is a word which means friendly/pleasant/agreeable. It is therefore a positive word when used to describe something.
If someone is amiable, they're pleasant and easy to get along with- the word has a positive connotation attached to it.
good, excellent, pleasant, lovely, beautiful, agreeable, nice-looking, amiable,