A quick oneshot I got from seeing a T-shirt saying: 'A significant factor in Lord Voldemort's rise to power is that the Doctor didn't stop him.'

No particular Doctor

"I address the Chitauri according to article 16 of the Shadow Proclamation. This is a level five planet, you WILL cease your attack on Earth, you WILL return peacefully to where you came from, or I will stop you. I am the Doctor, Oncoming Storm and Destroyer of Worlds and you WILL get off my adopted planet, or I will erase your entire species from existence, in every universe, in every dimension. Do. I. Make. Myself. Clear?"

Silence. The Avengers looked at each other uneasily. This man seemed even more of a threat than the aliens.

The stranger leaned forward and whispered into the microphone, staring straight at the screen.

"Run. NOW."

It was almost comical how one man wielding words and titles like a sword made every last Chitauri warrior flee with their tails between their legs.