The name No Mercy In in Chinese / Japanese...

水火無情 is a Chinese proverb that means “fire [and] water have-not mercy.”

This serves to remind us that the forces of nature are beyond human control.

Some may also translate this as “implacable fate.”

觀音/観音 is the Buddhist deity known as the Goddess of Mercy or Bodhisattva of Compassion.

In Chinese, the proper name of this being is Guan Yin. There is some debate as to whether Guan Yin is female. The argument comes from some scripture that suggests Buddhist deities take on the male form. Others say that Guan Yin has no sex. And still, others are okay with the female representation of Guan Yin.

This bodhisattva is also known or Romanized in the following ways:
Mandarin Chinese: Guan Yin, Kuan Yin, Kwan Yin.
Japanese: Kannon, Kwannon.
Sanskrit: Bodhisattva Avalokitesvara.
Korean: Gwan-eum.
Vietnamese: Quan Âm.
Thai: Kuan Eim.
English: Bodhisattva of Mercy and Salvation, Goddess of Compassion, Buddha of Mercy, et al.

Note: The first character has a slight variation in Japanese. If your audience is specifically Japanese, you may want to select that version.

See Also:  Buddhism | Goddess | Namo Amitabha | Bodhisattva

無情 is a terrible phrase for a calligraphy wall scroll. I'm not even sure any of my calligraphers will write this. It's just that many people have searched my website for “no mercy.”

This word means pitiless, ruthless, merciless, heartless, heartlessness, hardness, cruelty, or ruthless.

In the context of Buddhism, this is used to describe something or someone that is non-sentient (inhuman or without feeling).