My Ipad 2 does not want to charge: how should i fix it?
Your question is a little vague but we can make a few suggestions based on what it could be.


Replace the charger and cable with a new charger and cable. If the charger went bad (and a cable could masquerade as a bad charger) replacing it (or testing it) with a new one of each should narrow down the problem.
I don't know what "the opposite of charging" means. But if the iPad powers off when you unplug it I would think item one above isn't gonna help as the charger/cable are providing power to the iPad. That might indicate a bad/worn out battery.


Note that the indication that it might be other than the battery (replace the lightning port or logic board) is possible. 

Honestly I would take it to a trusted independent service center and see what they say.