Machiavelli's 3rd instruction

Third instruction to maintain power and preserve order: When can a ruler enter into evil -  "if necessary" and when all other options fail.

• Pointing to his sister as a negative example, Tyrion suggests that an overreliance on fear presupposes an overuse of cruelty.  
• Once a ruler's actions fatally blur the fine line that separates fear from hatred, as Cersei's have done, maintaining power becomes increasingly difficult because popular favor deteriorates.