This particular rare nevi is the easiest to beat. He appears as one of the small nevis but don't under estimate him. Like the other rare nevi, he too is outlined in green.
This rare nevi can be found in The Ruins area. In the center of the area there is a large pillar. Fly to the bottom of this pillar and underneath it there is a hole that leads up into the pillar. The rare nevi is in there. Look at the pictures below for visuals as to the location.
Hopefully this nevi will not be too hard for you to beat. It is recommended that you have your kick and gravity kick to at least level 3. When you are too far away for the nevi to melee attack you he will send masses of gravity balls towards you. You can use the dodge to avoid these however you will need it upgraded very high in order to dodge fast enough. Getting around these can be hard which is why its recommended that you stay close to it where it will not attack you. While on the ground just keep tapping the kick button while dodging whenever it is about to attack. There are several health orbs located around the area that you can pick up but know that if you get too far away it will shoot out the gravity balls again. Instead, try to move towards them slowly so that the rare nevi has time to follow you.
Just repeat the process of kicking and dodging until eventually you destroy it.