There are many ugly buildings in Chicago, but it is really just am opinion.
Here are some other views about the topic from TravelandLeisure.com:
If buildings came with footnotes, this one, named for a beloved former mayor who deserved better, would have pages worth of citations. Neoclassical references collide with a glass-and-steel Mannerist roof; throw in some red brick, granite, and aluminum—and a bad sense of scale—and you’ve got way too much architecture class for one day.
The Ugly Truth: Opened in 1991 and designed by the firm Hammond, Beeby, and Babka, the Chicago public library has a helter-skelter application of motifs and styles that’s “locked in the postmodern era,” says Peter Koliopoulos of Circle West Architects in Scottsdale, AZ.