Social distancing and isolation will stem most infections, so 'deadliest' a long time ago was much more than now.
For example, AIDS- stop fooling around!

Just to cheer everyone up, covid-19 kills 1% of those who get it, but they have discovered a corona virus that spreads from animal to human but not from human to human that kills 75%, watch this space for nature's revenge when it mutates to one that can!