The word "deadliest" is correct and usable in written English.
You can use it to describe something that is more deadly than something else. For example, "This is the deadliest virus we have ever encountered."
Researchers have also found that climate change-enhanced heat and humidity are conducive to the spread of falciparum malaria, the disease's deadliest strain.
Amnesty International described as the terror group's "deadliest massacre" to date, and local defence groups said they had given up counting the bodies left lying on the streets.
The grim death toll in the Mediterranean has provoked a chorus of calls for action to prevent 2015 becoming the deadliest year for migrants trying to get to Europe.
Best's deadliest trick was to take the ball so close to a defender that when he beat him recovery was impossible, and after about 15 minutes of his debut he body-swerved Williams into performing a complete blundering circle.
Stage five is the mysterious sickness in its deadliest form.
Israel killed dozens of Palestinians in a Gaza City suburb in the deadliest attack in an almost two-week offensive against Hamas.
India is thought to have some of the world's deadliest roads, with an estimated 1.2 million fatalities over the past decade - that's one every four minutes.
Annual rankings from the Committee to Protect Journalist published earlier this year named Syria as the deadliest place in the world to practise journalism and in 2013, it joined a list of countries where the murder of journalists was likely to go unpunished, for the first time.
It was the deadliest such confrontation in recent memory and followed two deadly clashes in the area controlled by the powerful Jalisco New Generation cartel.
More than 101 people were killed and nearly 600 wounded; it was one of the deadliest attacks in the six-year-old Iraqi insurgency.
One by one, individuals collapsed in agony and within days, around 200 were dead, victims of the deadliest and swiftest outbreak of cholera ever to have struck Britain.
