adverb
mercilessly; ruthlessly
Adverbial form of 情け容赦ない, meaning without mercy or pity; used in formal or emphatic contexts.
彼は情け容赦なく敵を攻撃した。
He attacked the enemy mercilessly.
上司は情け容赦なくミスを指摘した。
The boss pointed out the mistakes ruthlessly.
容赦なく is a more common and slightly less intense adverb meaning 'without mercy' or 'relentlessly'. 情け容赦なく adds 情け (sympathy) for extra emphasis on pitilessness.
Compound of 情け (sympathy, mercy) + 容赦 (pardon, forgiveness) + なく (adverbial form of ない). The combination reinforces the sense of complete mercilessness.