Expression
Verb (5-dan, る, intransitive)
1. to get worse; to deteriorate; to go from bad to worse; to become worse
あなたさえいれば何も悪くなるはずはない。As long as you are here, nothing can possibly get worse.
2. to spoil (of food); to go bad; to perish
お魚はすぐ悪くなるから。Fish spoils quickly.