letting die without helping; standing by while someone dies
Implies a moral failure to act; often used in serious contexts such as accidents, crimes, or social issues.
It's unforgivable to just stand by and let someone die at an accident scene.
He let his drowning companion die without helping.
He was accused of letting the drowning person die without helping.
Many patients were effectively left to die because of the hospital's slow response.
Feeling he couldn't just let his friend die, he went to help.
放置 means leaving something unattended or neglected without necessarily involving death, while 見殺し specifically means failing to prevent a death one could have stopped.
皆殺し means massacring everyone, while 見殺し means passively letting someone die by not helping; the two words look and sound similar but describe very different acts.
A noun derived from 見殺す, formed from 見る and 殺す in the sense of watching someone die without intervening.