He appeared like a phantom, his arms readying themselves to pierce Remira's head. This was an opportunity that only a fool would forego.
Remira Wyrmwood was a nuisance to his creator for a long while, but Rosso rarely held any hatred for her due to the memories he held. To him, she was nothing more than a fool that is prone to making mistakes.
Someone born with a silver spoon that only survived due to his Creator's kindness. But that all changed in Rudrain, the fight he had there made him aware of certain things. 'Don't look down on them.' Even if she is a fool, she is still stronger than him and holds the intent to suppress or end him.
Making her a dangerous enemy and considering there was nothing about not killing this fool of a woman, why should Rosso hold himself back?