Ruthlessness and Unmercifulness

Ruthlessness noun - Mercilessness characterized by a lack of pity.

Unmercifulness and ruthlessness are semantically related. In some cases you can use "Unmercifulness" instead a noun "Ruthlessness".

Unmercifulness noun - Inhumaneness evidenced by an unwillingness to be kind or forgiving.

Ruthlessness and unmercifulness are semantically related. Sometimes you can replace term "Ruthlessness" with "Unmercifulness", this nouns are similar.