halacha - What degree of punishment is assigned to one who wants to commit a sin, but is only stopped by the lack of an opportunity?

For instance, if one thought of murdering a certain someone, but the only thing stopping him was the lack of an opportunity, would he be liable to a punishment equal to that of a murderer, or something lesser? Is there no punishment at all?

Is there a difference between an individual who would commit the sin of his thoughts versus one who wouldn't?

This question came to mind after the subject of freedom of choice came up on Shabbat at the synagogue. If someone were to wish, like Hitler, that they could wipe out all the Jews, but the only thing stopping them is a lack of opportunity, would their punishment be equal to his (whatever it is)?