“Avengers: Infinity War” held the top spot at the box office for the third week in a row, easily dispatching feeble challenges from two newcomers pegged to Mother’s Day, “Life of the Party” and “Breaking In.”

“Life of the Party,” a Warner Bros. comedy in which Melissa McCarthy goes back to college, opened to $18.5 million, according to comScore, which compiles box office data. It was one of the lowest openings for a movie starring Ms. McCarthy, and paled in comparison to “The Heat” ($39 million in 2013) and “Spy” ($29 million in 2015). “Life of the Party,” directed by her husband, Ben Falcone, cost about $33 million to make and at least that much to market; it was marred by mediocre reviews and a B from CinemaScore exit polling.

Universal’s thriller “Breaking In” came in third with $16.5 million. The film follows Gabrielle Union as a mother trying to rescue her children who are being held hostage by intruders in her house. It was a good start for the low-budget film, which cost an estimated $6 million to make.

Of course, “Avengers: Infinity War” still reigned supreme, taking in another $61.8 million domestically. It opened in China to the tune of $200 million, and has now reached $1.6 billion total globally. The film will receive its first real challenge next week, when “Deadpool 2,” another Marvel film, arrives in theaters.

And Lionsgate and and MGM’s “Overboard” came in fourth with $10.1 million. The film, which features the Mexican star Eugenio Derbez opposite Anna Faris, earned slightly more than that in Mexico, where it topped the box office in its opening weekend as “Hombre Al Agua.”