Which word describes someone who is overly content and self-satisfied?

The word that describes someone who is overly content and self-satisfied is "complacent." This term refers to an individual who is so satisfied with their achievements or situation that they become unaware of potential dangers or deficiencies. A complacent person may lack the motivation to improve or change their circumstances because they feel too comfortable in their current state.

In contrast, "defamation" refers to the act of damaging someone's good reputation, "explicate" means to explain or analyze something in detail, and "pandemonium" describes a state of chaos or uproar. These definitions clarify why "complacent" is the most fitting word for describing an individual who is excessively pleased with themselves and their situation.