Harry found out that Ron, Dumbledore, Ginny and Molly were cheating him, and he feeds a potion that weakens magic, eventually turning the wizard weaker and to a squib to dumbledore.

He doesn’t do it himself.

But, I forgot who was helping him.

This potion is fed to Dumbledore by lacing his lemon drops candy.

Please help me.

I just know that this was posted in fanfiction.com.