destructive · harmful · damaging

Read, every day, something no one else is reading. Think, every day, something no one else is thinking. Do, every day, something no one else would be silly enough to do. It is bad for the mind to be always part of unanimity.

A doctor told me that eating eggs was bad for me.

There's a chance that tap water may contain harmful substances like chlorine and lead.

It is clearly shown in Johnson's investigation that passive smoking is very harmful.

Smoking kills.