Poisonous (adjective)

1. Containing or producing poison; harmful or toxic.
2. Having a harmful or malign effect on the mind or character.

Origin:

Late middle english: from old french poisonnus, from poison (see poison).

Examples:

1. The mushrooms are poisonous and should not be consumed.
2. The snake has a poisonous bite.
3. The air was filled with poisonous fumes.
4. The advice he gave was poisonous and caused more harm than good.
5. The relationship was poisonous and needed to be ended.