An act or feeling that shows no pity or compassion can be described as merciless.
When we describe someone or something as merciless, it means they don't care about how others are affected. For example, a ruthless business owner who doesn't care about his employees' well-being might be called merciless. A critic who savages an artist's work without any kindness would also fit this description.
Showing no mercy; cruel and pitiless.
