Negative energy is a feeling that you get when your around certain people; this feeling tends to be putting you down and in a bad place. Most people try to avoid negative energy by ditching the people who bring them down and are rude to them.

1. Everyone gives off an energy, or aura when you are near them. Like think like this, some people give off a positive aura which fills you with happiness and amicableness(not sure if that’s even a real word) while a person with negative aura fills you with gloom and steel-headedness(also not sure if this is a real word). These are all influenced by their actions, which are in turn influenced by their emotions, so negative energy basically would mean any bad emotions like hatred or sadness or fear... etc.

2. It’s also used quite often in modern anime as a superpower the MC or close relation has in which it’s usually activated when the character is close to death or full of rage at the death of a loved one. Many cosmetic effects of the negative energy effecting the character include but are not limited to: lightning of any sort, usually blue or purple, dancing around the character: crimson fire appearing behind them: their body being covered in black shit from god knows where: their muscles suddenly expanding and then ripping apart to reveal that they now have a giant skinless arm with metal blades attached somehow: and, last and probably least, their eyes turn black, red, orange, or purple

3. The weapon of the main character and his friends in the book series World Tree Online that they use to conteract positive energy, which is being enslaved and harnessed by a corrupt god for purposes it was not intended to be used for.