Now that was a challenge to his manhood. 'Not a professional, undead assassin' Tony could live with, but 'frail'? Baby birds were frail. Tony Stark commanded the technological advancements of the modern world with a wave of his hand. He was 185 pounds of-- well, he had been slacking lately, without the Captain around to keep him in top form. Still, most of those 185 pounds were solid muscle, trained to defend by Captain America himself. Frail was just downright insulting.
His eyebrows raised, just as he raised to the challenge, unmoved as she stepped in. He just squared his shoulders and tilted his chin up, taking advantage of his height with a cocky grin that he didn't entirely believe in. She was still the professional, undead assassin. But she did have one arm behind her back. So he made to grab for the other, putting an arm between them as he did.