A frustratingly not-terrible action thriller.
"What's the Worst That Could Happen?" has too many characters, not enough plot, and a disconnect between the two stars' acting styles. Danny DeVito plays a crooked millionaire, Martin Lawrence plays a smart thief, and they seem to be in different pictures. DeVito as always is taut, sharp, perfectly timed. Lawrence could play in the same key (and does, in an early scene during an art auction), but at other times he bursts into body language that's intended as funny but plays more like the early symptoms of St. Vitus' Dance.
Comedy tradition holds that onlookers should freeze while the star does his zany stuff. From Groucho Marx to Eddie Murphy to Robin Williams to Jim Carrey, there are scenes where the star does his shtick and the others wait for it to end, like extras in an opera. That only works in a movie that is about the star's shtick. "What's the Worst That Could Happen" creates a world that plays by one set of comic rules (in which people pretend they're serious) and then Lawrence goes into mime and jive and odd wavings of his arms and verbal riffs, and maybe the people on the set were laughing but the audience doesn't, much.
The plot involves Lawrence as a clever thief named Kevin Caffery, who frequents auctions to find out what's worth stealing. At an art auction, he meets Amber Belhaven (Carmen Ejogo), who is in tears because she has to sell the painting her father left her; she needs money for the hotel bill. She has good reason to be in tears. The painting, described as a fine example of the Hudson River School, goes for $3,000; some members of the audience will be thinking that's at least $30,000 less than it's probably worth.
If Kevin is supplied with one love interest, Max Fairbanks (DeVito) has several, including his society wife (Nora Dunn), his adoring secretary (Glenne Headly) and Miss September. (When she disappears, Max's assistant Earl (Larry Miller) observes there are "11 more months where she came from"). Kevin also has a criminal sidekick named Berger (John Leguizamo), and then there is his getaway driver Uncle Jack (Bernie Mac), and a Boston cop (William Fichtner) who is played for some reason as a flamboyant dandy. If I tell you there are several other characters with significant roles, you will guess that much of the movie is taken up with entrances and exits.