The Nega-Bomb is a powerful bomb created by the Kree. It is designed to destroy everything and everyone in its planetary-wide blast radius.
Each Nega-Bomb is implanted on each Sentry on their travels to targeted worlds on their mission to disarm and destroy the inhabitants' resistance.
The Kree Sentry-459 has such one Nega-Bomb inside its chest in in its exploration on Earth. Given the fight the Avengers put up against it,the Nega-Bomb will charge up and then explode.
But the Sentry was destroyed by the Avengers assisted by Captain Marvel, and the Nega-Bomb was thrown into space where it exploded harmlessly near the moon by Thor.
It is unknown if the Nega-Bomb practice remain or discontinued by the Kree.
Background in other media