@Solitude  
He’s laughing now but wait till they fly a spaceship through one of his eyes, give him the worst case of indigestion he’s ever had and drive out through his other eye. Also, Dinobots.
 
_{Slight improvement.}

He’s laughing now but wait till they fly a spaceship through one of his eyes, cause him to spontaneously combust from the inside and drive out through his other eye. Also, Dinobots.

Interesting combination, but I’m not sure how it would work, considering Discord, at heart, is nothing more than a prankster, while Unicron is an ultimate evil in his own right. To get a better idea of what I’m getting at here’s an excerpt from “The Transformers My Little Pony Crossover 2” (copied and pasted from TVTropes)
 
[A flash of light blinded Discord, and he found himself back in the Canterlot throne room. He was on his knees and hands, hyperventilating, shaking. He looked up. Galvatron, Cyclonus, and Scourge were glaring down at him.]  
Discord: W- what… was that?  
Galvatron: That, was Unicron. He is the true Chaos Bringer. He has devoured countless worlds, killed trillions of lives, and is among the most powerful beings in existence.  
Discord: But what about me?! I’m the Spir-  
Galvatron: You are nothing but a clown!  
[Discord flinched.]  
Galvatron: Do you hear me? You are nothing but a sad, pathetic, clown. A bad joke.  
Discord: B- but I-  
Galvatron: You know nothing of chaos. And do you know why? Because you are not chaos. You saw my memories. That was true chaos. Your little tricks? Pathetic.  
[Discord felt something within himself begin to change, as if his whole purpose in life had been suddenly extinguished. He did not realize it, but the color of his body changed from its usual bright pigments- to a dull grey.]  
Galvatron: And now, you will die for wasting my time.

What will he do with the death star?

Except he does it for shits and giggles, and to watch the little ant creatures and ponybots scramble around in a panic.

“For a time, I considered sparing your beloved little planet, Equestria. But now, you shall witness… its PANDEMONIUM!”
 
“NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO”