He has made so many threats over the years to so many people, yet now he claims it is all made up. Really think there is mental issues at play.
I generally ignore him as there is typically nothing you can accomplish when dealing with such a person.
If something does go to legal, then Slack can be subpoena for the full logs. There are some really good ones I haven't shared as they are not my own interactions and many got wiped as Ned has the retention rules at 30 days by default.