Since becoming commissioner, Mr. Vincente has snapped at the heels of the dominant firms in European industry more __________ than his smoother predecessors and has consequently acquired many more enemies.
He has snapped at the heels of the dominant firms to a
greater extent than his smoother predecessors. We know this because he acquired many more enemies. But we need more precise words, "greater extent" is too general and gives us only the magnitude, which we know was greater.
The phrase "smoother predecessors" implies he was kind of rough.
So
irascibly and
pugnaciously are the right choices. They are not exactly synonyms, but they are the only ones which convey a
greater aggression implied by the sentence, especially by contrast, through the phrase "smoother predecessors".
_________________