What do you call a person who does anything to get something?

Solution 1:

unscrupulous seems like a good adjective for Macbeth's character.

"not controlled by one's conscience and contemptuous of what one knows to be right or honorable" TFD

• "an unscrupulous landlord".
• ""unscrupulous politicians who would be happy to sell their country in order to gain power"

Having or showing no moral principles; not honest or fair: unscrupulous landlords might be tempted to harass existing tenants. ODO

Solution 2:

ruthless

"Some ​people ​believe that to ​succeed in this ​world you have to be ruthless."

(not ​thinking or ​worrying about any ​pain ​caused to ​others) http://dictionary.cambridge.org/dictionary/english/ruthless

The example given is 'Macbeth's character is very ambitious but also...'

"Shakespeare’s Lady Macbeth: Manipulation & Ruthlessness"

http://schoolworkhelper.net/shakespeares-lady-macbeth-manipulation-ruthlessness/

Solution 3:

hell-bent

: stubbornly or recklessly determined.

Random House

Solution 4:

"Machiavellian", willing to employ immoral and/or dishonest means to achieve political power. Ruthlessly manipulative.

"He was willing to employ Machiavellian tactics in order to win the election."

The word refers to Niccolò Machiavelli, who is well-known for writing "The Prince," a Renaissance-era treatise on the attainment of political power.