What other words could you use instead of very bad?

Here are some alternatives to "very bad" depending on the context and level of severity you want to convey:

Mild:

* Poor

* Unsatisfactory

* Subpar

* Mediocre

* Disappointing

* Not good

* Lackluster

* Unfavorable

* Incompetent

Moderate:

* Terrible

* Awful

* Dreadful

* Horrible

* Abysmal

* Appalling

* Deplorable

* Disastrous

* Catastrophic

* Tragic

Strong:

* Despicable

* Reprehensible

* Heinous

* Abominable

* Devastating

* Degrading

* Monstrous

* Outrageous

* Unforgivable

* Criminal

Informal:

* Lousy

* Crap

* Rubbish

* Lame

* A disaster

* A nightmare

* A total bummer

Specific to situations:

* For health: "Poor condition," "Serious," "Life-threatening"

* For performance: "Substandard," "Inefficient," "Unacceptable"

* For behavior: "Inappropriate," "Disrespectful," "Unforgivable"

* For ideas: "Unsound," "Flawed," "Impractical"

Remember: The best word to use will depend on the specific situation and the message you want to convey.