Here is what Judd Apatow and Paul Feig know that Melissa McCarthy and Ben Falcone do not: a character can be hilariously obnoxious or endearing but not both, even when played by the irresistible McCarthy. Apatow and Feig have made the best use of Melissa McCarthy’s endless comedic talents, and it is instructive to see how they did it. In “Bridesmaids” (produced by Apatow, directed by Paul Feig), McCarthy played a strange woman with some social deficits but capable (she was right about the air marshall, played by Falcone, who is her husband and co-screenwriter and director of “The Boss”), loyal and self-aware. In “Spy,” written and directed by Feig, McCarthy is awkward and deferential, but she is capable and brave, and she knows it. In “This is 40,” McCarthy has a small role as an angry mother complaining about the main characters’ child. Her fearlessness and improvisational skills, highlighted in a post-credit sequence, were a highlight of the film.

She gave a thoughtful performance in a dramatic role as a single mother in “St. Vincent,” and she was wonderful as a cheerful chef in “Gilmore Girls.” But in other films, including “Identity Thief,” “Tammy,” and now “The Boss,” McCarthy makes the fundamental mistake of committing to an obnoxious character given to outrageous and inappropriate behavior and then insisting that by the end of the movie the other characters and we in the audience have to love her. If she wants to play characters like that, the narrative of the movie has to be about thwarting or triumphing over her in some way. But she can’t insult and cheat everyone for ninety percent of the movie and then expect us to hope for her to have a happy ending.

In “The Boss,” McCarthy plays Michelle, the 47th-richest woman in America and the CEO of three companies, at least one of which seems to be either a shady multi-level marketing scheme or some sort of “let me show you how to be rich scam.” She comes out to screaming applause from a huge crowd to brag about her wealth. Nice touch: some of the audience wearing Michelle-style red pixie-cut wigs. Less nice touch: she raps along with T-Pain. Michelle is rude to everyone and ruthless in business to a ridiculously counterproductive degree. For example, she brags to her rival (and ex-boyfriend) that she is making a fortune based on some insider information, which he then reports to the SEC, and which then gets her thrown in jail, Martha Stewart-style.

Five months of a country-club prison equipped with tennis courts (and, apparently, a manicurist because she has professionally done French tips), Michelle discovers she has lost her jobs and all her money. She drags her Vuitton luggage over to the apartment of her level-headed former assistant, Claire (a game Kristen Bell), a single mom with a daughter named Rachel (Ella Anderson). When Michelle tastes Claire’s delectable brownies and sees Rachel’s Dandelions troop (think Girl Scouts or, more accurately, think Troop Beverly Hills), she sees her path to a return to moguldom.

McCarthy, swathed to the chin in turtlenecks that make her look like she is recovering from whiplash, gives herself a one-note role. She is mean, she cheats, she says wildly inappropriate things to children, and she is selfish to a sociopathic degree. Michelle the character and McCarthy the co-scriptwriter give those around her very little to do, criminally under-using Bell, Kathy Bates, Margo Martindale, and Kristen Schaal. Peter Dinklage, as Michelle’s former colleague and boyfriend-turned rival is a bright spot, having a lot of fun going way over the top with pretentiousness, competitive fury, and lust. There’s an “Anchorman”-style rumble between the raspberry beret-topped brownie girls and their cookie-selling former troop. There’s a clever joke about finding just the right place to sell the brownies and there are a couple of very funny lines. But Michelle wears out her welcome very quickly and the resolution is unearned and cloying.

NOTE: There is an “unrated” DVD release. It is hard to imagine how much more offensive it could possibly get.

Parents should know that this film includes extensive strong and crude language, often directed at children, very crude sexual references, drinking, drugs, and comic peril and violence.

Family discussion: How did Michelle’s childhood experiences affect her relationships and priorities? What were the qualities that made her successful in business?

If you like this, try: “Spy” and “Bridesmaids”