This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Not feeling or showing pity.

Having no pity; showing no compassion.

adj. without mercy or pity

"But not even this induces us; more foolish are we than any, putting golden necklaces about our servants and mules and horses, and neglecting our Lord who goes about naked, and passes from door to door, and ever stands at our outlets, and stretches forth His hands to us, but often regarding Him with unpitying eye; yet these very things He undergoes for our sake."

merciless    unmerciful