If Kha'Zix somehow killed Aurelion Sol...

http://memesvault.com/wp-content/uploads/Wait-What-Meme-10.jpg

Brb, building a star proof underground shelter

He adapts to the prey he consumes and not transforms into it. He might learn to levitate, control stars in some fashions or "only" get a power boost, but he won't suddenly gain all of his powers.

I don't know, but I'm certain that Kha'Zix would burn his mouth quite badly.

Now he's PERFECT Kha'Zix.

"A bug? Kill ME? HA, I'd have to go down to the power level of low-flame for that mediocre lifeform to be even able to scratch me."

Plus, even if Kha'zix does do what you say, he wouldn't be able to handle Sol's power. It's like a solar panel absorbing all the power of the sun. It'd be overloaded.

well a squrel with a blowgun can kill sol, he probably isnt that powerful

It would have to be the other way around. Kha'Zix adapts to his prey in order to hunt them down and kill them. So, he'd have to evolve the necessary traits to take down a star dragon in order to kill Aurelion Sol.

So rather than gain all his powers, he'd probably be more of an antithesis to a celestial being. All the traits necessary to kill one.