Subtle characterization is a wonderful thing. Unsubtle characterization . . . not so much. There are a number of tricks for quick-and-dirty characterization, useful mainly in those forms and media where screen time or word count is tightly limited and strictly enforced; one of the down sides to becoming a writer is that one also becomes entirely too quick for comfort at spotting these tricks in action.
Possibly the most famous of these tricks is the old Hollywood advice for writers of westerns: When your villain comes to town, have him get off the stagecoach and kick the nearest dog.
A bit more subtle — but still not much — is characterization by significant accessory. I read a mystery novel once where the author tipped the readers off that they weren’t supposed to like a particular character by noting with disapproval that he owned a leather couch. (I gave up on that mystery series not long after, when I started noticing that the author appeared to feel more moral concern for crimes against animals than for crimes against people.)
Then you get characterization by opinion, which results in the sort of book where all the good characters share the writer’s political (or other) opinions, and win all the arguments, and all the bad characters espouse the completely wrongheaded opinions of the other side, and generally not only lose the arguments, but meet bad ends. There was, for example, one well-known mystery writer (now deceased) whose villains I could almost always identify before the final reveal, simply by noting which character in the story had committed the most egregious offenses against feminism. At the opposite end of the spectrum, there’s an entire subgenre of science fiction in which staunch (and usually gun-toting) conservative protagonists have to save the world from the bumbling mistakes, or even the downright treachery, of woolly-headed or hypocritical liberals.
None of these tricks are of their nature inherently bad. They’re bad because they’re exaggerated and obtrusive versions of techniques which, when done with a delicate hand, use telling details of setting and behavior to illuminate the truth. As so often in writing (and art in general), the thing that matters isn’t what you do, but how you do it.