Throughout the 12 episodes of the Devil May Cry anime, Dante never (or never clearly) activated his devil trigger where he turns into his more powerful devil forms. We can tell that the Anime takes place after the events of the 1st and 3rd Devil May Cry games since Dante is already acquainted with Lady and Trish, so Dante should have already long been able to activate his Devil Trigger. In the anime, it seemed there was barely ever a need for Dante to use his devil trigger as most of his enemies were able to be defeated with his fighting skills even as a human. In the last episode though as the final blow was being dealt to the hosted Demon Abigail we get a closeup of Dante's eye as a flash of red light/energy fills the screen.
Similarly in video games, a flash of red light appears as Devil Trigger activates. However, Dante's physical features should completely change into a more demonic appearance such his skin turning black and eyes glow a yellow color. Dante's sword Rebellion is able to create waves of red energy so it's possible it could be just this. So did Dante really activate his Devil Trigger in the final episode of the anime?