1. worst

noun (common) (futsuumeishi) adjectival nouns or quasi-adjectives (keiyodoshi) nouns which may take the genitive case particle 'no'

2. horrible, horrid, awful, terrible

interjection (kandoushi) adjectival nouns or quasi-adjectives (keiyodoshi) colloquial

3. in the worst case, if worst comes to worst

adverb (fukushi) colloquial