I am yet to watch Pan's Labyrinth but Anton at least seems to have some twisted sense of honor (even if it's not disqualifying because it's motivated by his desire to kill) and he also spares some of the people he encounters.

So, I choose Vidal.

Well… when it comes to PEs, Anton is an anomaly. Excuse the upcoming walls of text, but I believe they are necessary in clearing up any potential misconceptions.

He isn’t really honorable so much as he is driven by his own outlandish fatalistic code; in the case of sparing a select few individuals, he gives them a chance to live via coin toss because he subtly sees himself as the culmination of one’s life choices and errors—hence getting them to call it rather than simply leaving it to chance like, say, Two‐Face does with his coin tosses. That is Anton’s rationalization; his killings—be it of criminals and otherwise targets who deserve it / whom he would benefit from killing (e.g. cartel members, his own employer in the film, Carson Wells, Llewelyn Moss [attempted], etc.), or of innocent randomers who either somehow violate his code or aren’t at all an obstacle (e.g. the store clerk [almost], Moss’s wife)—are justified in his mind by virtue of being the outcome of their actions, what they themselves called the coin to land on.

More importantly, Anton, being a fatalist, genuinely seems to believe that he has no say in what he is or does and that all the cruelty in his wake was predetermined; not only does he evidently have no real desire to kill Moss’s wife, but he also appears to be quite shaken up when she points out how he uses the coin (i.e. his ideology) to wash his hands of responsibility and that it really is all him, consciously or otherwise. Regardless, Anton is still clearly a man of principle.

What I believe makes him evil and dishonorable in spite of all this is that it makes no real difference to him whether those people he spares live or die (seeing that his cattle gun reflects his view of people after all) and how emotionless he is towards the deaths and suffering of others in general—but since Vidal lacks such complexity and we see how he disregards (and murders) his family while being about as cold as Anton, my vote goes to him.

Captain Vidal is much more terrifying than the monsters in the film.