It means that IF there had been a Highlander 2 I would forgive Highlander 2, but not the people who made Highlander 2. Fortunately that movie doesn't exist.
Deadpool 2 was excellent, even better than the first. The scene on the couch after Deadpool's unfortunate encounter with a certain villain whose name begins with 'J' is one of the most disturbing and hilarious in the entire history of cinema. ?