Alex's fight against the combined force of Kirche, Montmorency, Guiche and Tabitha. The awesomeness doesn't really comes from the fact he easily defeats them all (which was in itself pretty predictable) as much as the fact he manages to resist the urge to eat them, and spares their life even though his instincts are urging him to consume them all. This shows how determined Alex is to not be a monster.
In chapter 9, Alex cures Ill Girl Cattleya by creating a retrovirus inside himself that repairs her congenital organ problems without turning her into a Blacklight monster. For once, Alex uses his powers to save a life instead of taking it.