Meteor strike

Let's assume that there is a mad scientist, who wants to destruct the Earth because of a reason that no one know. He has a plan called "Meteor Strike". The plan is simply following.
First, he goes to Oort cloud at outer space of the Solar system. Second, he finds a meteor that is large enough to break the Earth. Last, he tracts it to the Earth.

Question : How much times will the plan be taken?

Considerations : His life time, technology, cost, and so on...