Aeris giving the Master his just desserts in The Last of the Time Lords;
As the chanting continued, the Doctor de-aged back into the wizened old man he'd been for the past year. "I've had a whole year to tune myself into the psychic network and integrate with it's matrices." he told the Master.
"I order you to stop!" the Master roared, storming down the stairs to Martha and Aeris.
Martha just closed her eyes and chanted "Doctor" even louder. Aeris meanwhile fixed the Master with a hard look, then, with lightning fast speed, she karate chopped him on the shoulder, knocking him to the floor.
"That's for all the evil things you've ever done." she snarled at his prone form.
Meanwhile, the chanting continued all across the world until finally the Doctor was restored to his normal youthful appearance. "The one thing you can't do, stop them thinking." he told the Master. "Tell me the Human race is degenerate now, when they can do this."
Martha ran over to her family, and they all hugged each other in relief, while Jack and Aeris both grinned at seeing their friend back to normal.
"No!" the Master screamed, firing a shot from his screwdriver at the Doctor, which was harmlessly absorbed by the telepathic field.
"I'm sorry." the Doctor said, "I'm so sorry."
"Then I'll kill them!" the Master snarled, turning his screwdriver on the Jones family.
"Oh no, you won't!" Aeris snarled. "Gimme that!" She wrestled the laser screwdriver from his grip and used her sonic screwdriver to destroy the Master's weapon.
"You can't do this!" the Master cried like a spoilt child. "It's not fair!"