Ani (아니) is rather for short answer with no honorifics and between friends or to someone younger. Aniya (아니야) is the same thing with expression and feeling and sounds good in a whiny accent. Anniyo (아니요) is proper for most situations. Eobseo (없어) is "I don't have it" or "It isn't there/here" or "He doesn't have it" whatever the context, you just understand. Eobseoyo (앖어요) would be more polite.

아 니 요