Big Ass Spider!

Big Ass Spider is a 2013 comic science fiction film directed by Mike Mendez. The film tells the story of a bug exterminator, who, with the help of a hospital security guard and the military, have to battle a giant spider that goes on a rampage in Los Angeles. It has received positive reviews from critics.

Meanwhile, the spider, growing exponentially, kills a paralyzed hospital patient. Back inside the vent, Alex stumbles upon a spiderweb and learns that it is highly flammable. Alex ventures into the hospital basement, where he has a confrontation with the spider. The spider is driven off by Karly and escapes into a grate down into the sewer, where it kills a homeless man. Alex, enamored with Karly, offers his assistance to Braxton, who declines, especially when Alex presses him for answers on where the spider came from. Jos convinces Alex to continue their pursuit as it could be the most important thing of their lives.The duo tracks the stillgrowing spider at a public park, where it kills dozens of people. Alex and Jos get the spider to chase their truck and lure it to the military. A huge firefight ensues, but the spider escapes into the nearby woods. Karly and a group of soldiers pursue it, but the spider ambushes them, kills most of the soldiers, and captures Karly. After Alex and Jos demand answers, Braxton reveals that they discovered alien DNA and hoped to use it as a growth hormone. However, a spiders nest was hidden in some test fruit, thus exposing the spider to the alien DNA and triggering its rapid growth. It is also revealed that the spider will soon start reproducing based on its size and their studies of the alien DNA. ........

Source: Wikipedia