Man's Best Friend (1994)

Reporter Lori Tanner (Ally Sheedy), investigating a story about animal cruelty, gains access to a facility where dogs and cats are the subjects of cruel experiments conducted by Dr. Jarret (Lance Henriksen). After seeing the conditions of the lab, Lori flees the building, but massive escaped dog Max follows her. Lori decides to keep Max as a pet, but the seemingly lovable canine is a genetically altered dog with unusual abilities and psychotic tendencies that set him on a killing spree.