Difference between Ruthlessness and Mercilessness

RUTHLESSNESS vs MERCILESSNESS: NOUN

The property of being ruthless
The state or character of being ruthless; want of compassion; mercilessness; insensibility to the distresses of others.
Feelings of extreme heartlessness
Mercilessness characterized by a lack of pity

Arrogance, Relentlessness, Tenacity, Callousness, Savagery, Viciousness, Inhumanity, Wickedness, Barbarity, Meanness, Brutality, Ferocity, Pitilessness, Cruelty, Mercilessness

Stubbornness, Cowardice, Doggedness, Opportunism, Boldness, Malevolence, Treachery, Fearlessness, Arrogance, Tenacity, Savagery, Wickedness, Barbarity, Brutality, Ferocity

Daniel reveals why so many kids can have moments of ruthlessness.
Therefore, although Macbeth is a great warrior, he lacks ruthlessness.
The 16th-century treatise is known for its detached ruthlessness.
Weinstein acquired a reputation for ruthlessness and fits of anger.
The Maunavhathu warriors were known for their fearlessness and ruthlessness.
But his alleged ruthlessness in dealing with opponents is legendary.
So, you would turn your ruthlessness against the empire?
Were you uncomfortable with that sort of ruthlessness ever?
My ruthlessness terrorized the competition and can sometimes offend.
"Daniel has strength and fearlessness and ruthlessness - but it's a ruthlessness that has a level of emotion to it," comments executive producer Maisel.

The monologue reveals not only the reasons for his disapproval of the behavior of his wife, but also exposes his mercilessness.
Lion King, and the friend of his sovereign he achieved a kind of succh de circomtance by the mercilessness of his satire.
There was never cruelty and mercilessness in the voice and eyes of the King of Conquerors.
Even the ancients puzzled over why the Assyrians did not capture Jerusalem despite his reputation for mercilessness.