I'd say no. There's no widespread knowledge or evidence suggesting that 'Killer Soup' is a real story. It could just be a creative idea or part of a fictional tale.
Jeff the Killer is purely fictional. It was created and spread through various online platforms and has no basis in real events. People just came up with the creepy tale for entertainment or to scare others.
The Alaskan Killer Bigfoot is a very controversial topic. Many local tales and some eyewitness reports suggest it might be real. But when it comes to scientific scrutiny, there are a lot of factors that make it hard to confirm. For example, the harsh Alaskan environment can play tricks on people's senses. Also, most of the so - called evidence like footprints can be faked or misinterpreted. So, while it's an exciting story, it remains unproven.
The 'Cobra Killer' could refer to different real - life events or individuals. One possible reference might be related to a criminal who has a particular modus operandi or a specific case that got media attention. However, without more context, it's difficult to be very specific about the exact 'Cobra Killer' real story.