Instead of saying that something is bad or very bad try to use more precise and interesting adjectives to describe things

An unpleasant, a foul, a disgusting smell

Appalling / Dreadful / Severe weather

An unpleasant/ a frightening/ a traumatic experience

poor / weak eyesight

A terrible/ serious/ horrific accident

A wicked/ an embarrassing/ a difficult situation

We were working in difficult/ appalling conditions

To refer to your health, you can say: I feel unwell/ sick/ terrible; I dont feel (very) well

In coversation words like teribble, horrible, awful and dreadful can be used in most situations to mean vey bad