Time For Vol.4 of our Manga

Zygarde hums lowly as it gathers cells. In bright green streaks of light these parts soar onto it, making the Legendary grow as it changes to 50% form. "IT'S FUNNY THAT YOU BELIEVE YOU CAN STOP ME," the Shiny Darkrai declares. "I HAVE THE POWER OF ANGE! I AM UNSTOPPABLE!"

"You may have the power of Ange, but I am Ange," the heterochrome counters, summoning her wings and horns. "I think I can deal with my own power."

Darkrai looks at her with much intrigue. "So that's why you have that unique aura," it says, not yelling for the first time of this conversation. "It all finally makes sense. Well, you should understand me then. You, too, want the world destroyed. We have the same goal. Help me and we can fix society together!"

Zygarde watches Ange closely as she considers this offer. She has to be honest, this is very tempting to the part of her that still seeks revenge. The side that no matter how hard she tries to get rid of won't go away. But after a bit of silence, she shakes her head. "No."

"No," the white nightmare questions, obviously insulted.

"That's right," Ange confirms. "You're right, we both want to fix the wrongs of this world. And used to I would have been all for this plan. However, I have came to realize that doing this is wrong. Not everyone is bad! We should find a better way to help society!"

"THE HUMANS HAVE CORRUPTED YOU," Darkrai tells her, back to screaming. "UNFORTUNATELY, THAT MEANS I MUST END YOU!"

It launches a giant Dark Pulse at Ange, but Zygarde gets in the way, easily tanking the hit. The heterochrome crouches down a bit and notices that the Mega Energy around them is seeping into her skin. As usual, she is subconsciously absorbing it. She smirks to herself.

Maybe I can slowly drain it, she strategizes. And it won't notice due to how focused it is on our battle.

She likes this plan and flies into the air, launching a double Light of Ruins at the Mega Pokémon. Darkrai takes the hit, obviously feeling it but ignoring it pretty well. It the fires a Shadow Ball at her, which she blocks with a wing.

"For something that is using my power you sure are weak," she taunts, doing a brief land to gather some of the energy. "I'm pretty disappointed!"

"DON'T YOU DARE DISRESPECT ME," her opponent screams, shooting a Dark Pulse at her. Ange counters with Oblivion Wing, causing a tiny explosion from the collision. Zygarde takes advantage of the smokescreen and blasts a Dragon Pulse through it, hitting Shiny Darkrai before it can see it.

"Nice hit," Ange praises as she shoots back off into the sky.

"Thank you," Zygarde replies, using Thousand Arrows.

"YOU PESTS," the terror exclaims, sending off a wave of power that knocks Ange out the sky and all the arrows aways. "I AM TIRED OF THIS," it tells them as it begins gathering power.

You said it is at 90% power

I understood that as it is Mega but not full power