The term "second-guesser" refers to a person who doubts his or her own decisions or the decisions of others. Antonyms for this word may include "confident," "decisive," "assured," or "certain." These people trust their own judgment and are not afraid to take risks or make decisions. They may also be described as "self-assured," "unwavering," or "bold." Additionally, antonyms for "second-guesser" may also include words related to trusting others, such as "trustworthy," "reliable," or "credible." These individuals are confident in their ability to make decisions and have faith in those around them.