A common question is if events can be fully deleted. Currently, events cannot be permanently deleted, however they can be removed from the channels (and of course edited).
Find the event in Slack
First find the event you'd like to remove. The easiest way to do that is type "/events" in the channel to see all the events posted. When you find the event, click "Show me details"
Next, you'll want to click the "Remove" button.
This will bring up a confirmation screen asking if you are certain you want to remove this event. Once an event is removed, it will generated a notification in the channel letting folks know you've removed the event. Once ready, click "Yes, remove it" to take this event out of the channel.