Will Smith plays John Hancock: drunk, bum, arsehole, and superhero. His attempts to "help" people cause millions of dollars of damage as he slams through buildings, etc. One day, he saves PR idealist - how'd you get that combination? - Jason Bateman, and Bateman decides to try to reform Hancock's image by way of thanks. Bateman's wife Charlize Theron is less enthusiastic.
What unfolds is a mildly amusing, but still affecting story, until it gets to the mid-point of the film and abruptly changes direction. Now Theron comes much more to the fore, and you get a different story, but I liked this one too. Certainly more than the turn I thought it was about to take.
I wouldn't recommend it, or buy it, but I didn't find it objectionable.