Of course, in order to make their main characters likeable, many screenwriters do, in fact, do just that – make their main character pet a dog at the beginning of the film, which is perhaps why the Jack Nicolson character in As Good As It Gets was so notorious, as he actually threw a dog down the trash chute on page one.
Other ways to get us on board with a main character is to show them with some special power. Yes, your main character should do some things poorly (this is what will humanize her) – but is there something that she does really well, some incredible talent she also has, which will make her irresistible?
Besides functioning to create a main character who viewers will actually be interested in watching the whole film through, a special power can also work alongside a flaw to help your main character get out of trouble. This is often the case in action-adventure films. Say, the main character is great at martial arts, which helps him (or her) get out of trouble, even if this flaw might be what actually leads him into trouble in the first place.
Another way to play with a main character’s special power, is to actually make your main character’s flaw into their talent or gift. This is especially important to do at the end of the movie. Think of Elle Woods in Legally Blonde. Here, you have this character who is so superficial and appearance-oriented. But it was her obsession with beauty that actually provided her the edge to crack the legal case in the end of the film.
I have heard script consultant and author of The Coffee Break Screenwriter, Pilar Alessandra, call this “synthesis.” What this means is that the main character begins the movie with a flaw, they overcome that flaw over the course of the second act, the final battle occurring at the end of act three – but it is actually the evolution of that flaw into something good, something the main character can use, that makes them fully formed, complete.