(verb)
to act against something and oppose its effect, thus making it harmless or ineffective, for example to disarm a weapon such as a bomb;
e.g. I wanted to neutralize the negative feedback they'd received, so I told them what they had done well. The bomb squad was able to neutralize the device before it exploded.
(verb)
to make something chemically neutral by balancing its acidic or alkaline character or electrically neutral by balancing its positive or negative character;
e.g. The medicine helps neutralize the contents of the stomach.
(verb)
to make a territory neutral and designate it as safe from being attacked, typically during a war;
e.g. Both armies agreed to neutralize the regions surrounding the nearby town.
(verb)
euphemistically, to destroy or kill something, especially in a military context;
e.g. They had a variety of tactics to neutralize their enemies.