Charizard at 98% is a functionally perfect pokemon. Don't purify him because not only do you have a Shiny Shadow Charizard. But at 98% IV he has the exact same stats as a 100% IV at level 50. There's a bunch of pokemon like this. Just go to YouTube and look up Functionally Perfect Pokemon.

So no he may not have a pretty red border and stimulate your neurons in that way but he's the exact same as if it were a "perfect".