You can only delete participants one by one from an event, or delete the entire event and it will go from their records. But say you accidentally import the wrong event onto people's records, there's no global change or delete to get it off their records.
This would be so useful for my organization as we invite 1,000's+ constituents to events. An intuitive system would allow us to mass delete participants just as we are allowed to mass add lists of constituents.