A "connotation" is the diverse and possible ways that the meaning of a word may be interpreted, either negatively or in positive way. The opposite of connotation is "denotation" which is the actual and literal word definition.
This being said, keep in mind that the connotation of a word may differ from speaker to speaker depending on what role the word plays in the sentence.
In the case of the word "rancorous", the connotation is negative because we already know that the meaning of the word is someone who holds a grudge against someone else. Hence the connotations may include
- vengeful, angry, unforgiving, grudging
Encomium is a high praise, which is a positive thing.
- ode, allegorical, heroic, eulogy, speech, pride/proud
Filial is something that relates to a son or a daughter. For this reason, the connotation is positive and connotes parental connection.
- paternal, related, of parental origin, brother and sister, familiar, connected
Something "exemplary" is defined by dictionary as "deserving of imitation", or to serve as a pattern. This connotation is positive in most of its usage.
- extraordinary, unique, initiating, model, worthy of praise
The adjective "contrived" refers to something calculated and planned ahead. Hence the connotation is negative.
- pre-planned, malicious, pre-meditated, intentional, mean, fake
A thesaurus is often better than a dictionary to correlate denotation and connotation in words. Use an online visual dictionary and you can get some solutions to these kinds of grammar/vocabulary specific questions.