characters of a story are its pillars when it comes to fiction writing, and therefore you need to take utmost care when you shape them. In order to make sure that your story is gripping, you need to give due credit to its protagonist and antagonist - both of which share a symbiotic relationship and can't exist without each other.
Simply put, the protagonist is most often the 'good guy' in the story, while the antagonist is the 'bad guy' in it. If either of the two are depicted as invincible, the story tends to lose fizz from the very word go. That may sound too obvious piece of advice, but this is one of the most common mistakes we commit when writing fiction.
In order to give due credit to the two most important characters of your story - the protagonist (the good guy - in most of the cases) and the antagonist (the bad guy/group/institution), you need to be well-versed with the ideology that they represent and how they differ from each other.
In the creative field, a protagonist is the central character around whom the entire plot of the story revolves. The term is derived from 'protagonistes' - a Greek word meaning one who plays the first part or the chief actor. While the protagonist is a good guy in most of the stories, he can be a bad guy (or an anti-hero) as well. If he is a hero, the audience is expected to share empathy with him and this has to be kept in mind when writing his character. If he is an anti-hero the audience will not have any sympathy for him and therefore the character has to be gripping enough to keep the audience interested.
While an antagonist need not necessarily be a person, the protagonist has to be a person (or a group of people) with a cause. The examples of protagonist in fiction is quite lengthy, and includes some of the most famous fictional characters including Harry Potter, Superman, Batman, etc. In