Unitainium? Is that canon in Transformers? Or do you mean that G.R.E.N.D.A.L armor on deviantart? Because that's not immune to a sonic screwdriver. Besides, the Sonic doesn't actually attack. It disassembles, or assembles.
Because, I'm made out of Unitrainium, which is immune to all sonic, and sound devices, iv'e thought of every thing.
Then you know how a sonic works, right? Unicron, no matter how advanced, is still one big piece of technology. And I've seen the Doctor modify pretty big pieces of tech before. Like that giant Walking Cyberman in England? If his Sonic can influence the programming of something like that, who's to say it can't influence Unicron's?
I'm a doctor who fan you know, he sends the atraxi away, But I ain't afraid of the doctor I can smash him like a bug, and I can also travel in time. Dont think I don't know about the doctor, cause I'm a Whovian
Someone call the Doctor. There's another world-eating ancient evil whose power needs to be turned in on itself.