Antonyms for "more sweetnatured" include terms that describe someone as ill-natured, disagreeable, sour, or hostile. A person who is not sweetnatured may be described as malicious, spiteful, bitter, or even malevolent. They may not possess a friendly disposition and could come across as rude or insensitive. Other antonyms include descriptors such as unkind, discourteous, inconsiderate, or unfriendly. It is important to note that antonyms are opposites, and while some of these terms may describe individuals who are not sweetnatured, it does not necessarily mean they are bad people. People have different personalities, and every trait carries its strengths and weaknesses.