Beginning screenwriters often make the mistake (as I often did) of thinking that it is enough to make the main character her own worst enemy without ever creating a worthy opponent. According to Hicks, indeed "the main character is always the antagonist because the character has yet to battle the unknown of the internal need." Nevertheless, Hicks goes on to profess:
In short, make sure you have a human (or at least an intelligent being) antagonist for your main character to grapple with. Sure, some disaster films make a natural disaster into the opponent. But I strongly advise you create an actual person the main character can be fighting against.
Without the pressure of outside dramatic circumstances and the
threat of an external antagonist, the main character will never have to deal
with the internal need. That painful battle has been successfully avoided so far, and the character will continue to ignore it unless forced into action by the insistence of the dramatic conflict.
Hicks goes on to make some interesting assessments about the most typical main character flaws that tend to be found in particular genres of film.
Oftentimes, in personal dramas, the missing attribute is a quality such as
compassion or forgiveness or even self-reliance which the character believes he or she has but does not.
I would also add that often in romantic comedies, the main character flaw tends to be commitment phobia. The main character is unable to commit -- even when she's found the perfect person -- until she is forced to see the light somehow and overcome that phobia.
On the other hand, in the action genre, Hicks says the internal need may just be a need to become courageous (the main character flaw then is fear) or actually commit "to a value that the character has declared but never tested." For example, the main character is hubristic, but when it really comes down to a situation in which she needs to be heroic, she is scared.