Perhaps frail and weak
Yes, probably more so than mere "thin".
A negative connotation is a descriptive word that implies an undesirable characteristic. A negative connotation of the word strange is the word weird.
This is a negative connotation.
anorexic, stick, or gangly
It is a negative Connotation
Denouncing has a negative connotation.
A beggar generally is a negative connotation.
Emaciated is a synonym of thin that carries the most negative connotation, suggesting extreme thinness often due to illness or malnutrition.
A word often had two meanings: its denotation refers to its dictionary meaning. But its connotation is the understood or implied meaning of the word, containing the emotions and beliefs that the word makes people think. The connotation is often the cultural meaning: for example, in American culture, the word "fat" is defined in the dictionary as overweight or obese. But its connotation is very negative; American culture is obsessed with being thin, so "fat" has a negative connotation.
Negative connotation of the word "difficult" could be frustrating or challenging.
The word "failure" typically has the most negative connotation in a sentence.
A negative connotation of the word "talk" could be gossiping or spreading rumors.