The difficult part was sitting still and watching the results.

Coming up with the idea turned out to be the most difficult part.

They are considered the most difficult part of the game.

This turned out to be the most difficult part of the project.

That was always the most difficult part of her job.

He had always known this would be the difficult part.

Now came the really difficult part of our little talk.

It will take more time, but the most difficult part is over.

Of course, the most difficult part was still to come.

This could be the most difficult part of the approach.