[Johnny S]

"Columbus unleashed bad luck on the world."

Thank you.
I thought active and passive voice are related to the order of the subject and the action.

[Joy M]

Active, because the subject of the sentence, Columbus, is doing to action. You could, though you wouldn't want to, make the sentence passive by making "the world" the subject:

"The world had bad luck unleashed on it by Columbus."

In the passive form, the subject has the action performed on it, rather that it itself performing the action.

[Mickey D]

It could not be more active. The subject is Columbus. He did something: unleashed. The object of his doing was bad luck. He unleached it, actively.

Passive version: Bad luck was unleashed by Columbus on the world.

[dyp]

passive because you are not stating yourself, you stated a name