confident person; self-assured person
Describes a person who has strong self-confidence, often with a nuance of being overly confident or even arrogant. Can be used both positively and negatively depending on context.
He's a confident person, so he doesn't get too down even when he fails.
Being self-assured, she speaks her mind clearly.
自信満々 is an adjectival phrase meaning 'full of confidence', describing a state or appearance, whereas 自信家 is a noun labeling a person.
Compound of 自信 (self-confidence) and 家 (person with a certain trait).