"Stay still and shut up. This will only hurt for a second."
Tony can be quite a charmer. He's charismatic and smooth-talking, good at manipulating people's emotions. He is self-absorbed and flighty as a summer breeze. Boredom is the most dangerous aspect of him-- he's bored very easily, and when he gets bored, he will do whatever he wants to amuse himself. And that usually means that the test subjects are in trouble.
He doesn't like you, and he doesn't care about your problems. He's rude, conceited, sarcastic, and not particularly pleasant to be around. But in the same strange way, Tony cares immensely what you think of him. He's obsessed with appearances. He wants you to like him, even as he injects poisons into your system. He pretends to be your friend.
Tony is a fashionista. He's obsessed with how he looks. He loves Italian coats and designer labels and crocodile-skin belts... if you wear sweater vests, or ignore a stain on your tie, or wear socks with sandals, he will slap you.
For all his faults, though, Tony knows how to treat a woman. He knows exactly the right way to make them buckle at the knees, the right things to whisper into their ear, the right way to brush their hair out of their face... he was quite the player in his youth, and never quite grew out of it. He finds being a tester immensely sexy. He gets off on it.
Needles, treadmills, electrical shocks, adrenaline pills, infusion pumps, medical lasers, MRIs, scalpels... the list goes on and on. On top of it all, a sickeningly cheerful attitude.