Final answer:
King Richard's line that best shows his belief in the use of force for power is "Our strong arms be our conscience, swords our law," reflecting his view that strength and weaponry guide his reign.
Step-by-step explanation:
The line from the passage that provides the best evidence that King Richard sees force as a legitimate means of taking and holding power is, "Our strong arms be our conscience, swords our law." In this line, Richard clearly indicates that physical strength and the use of weapons are the guiding forces for his actions, dismissing the idea of a moral compass guided by conscience. This belief is reflective of the Machiavellian view that the ends justify the means, and it underscores Richard's brutal approach to rulership and authority where might is upheld over ethical considerations.