Yeah, Gore Magala could be considered an antagonist at least since a lot of the problems in the story do come back to it and it does actively serve as an obstacle the main character and other hunters must overcome if they desire to continue their way of life. It also does actively attack them at points in the story even when it's not antagonized itself, and unlike examples like Deviljho, it doesn't seem to have a reason like hunger or survival instinct to them. The only reason I wouldn't say it's a full fledged villain is that it lacks goals and motivations in the same sense as others like Sigma or Myria, it's just a wild beast as far as we know and it's hard to call something like that a villain.
I will say though, it definitely does have the look of a villain to it:
The Dark colors, the cape-like wings, the creepy atmosphere it brings to itself, it's basically how a classic villain would look if you made it into a Monster in the series.