There are a variety of ways in which I would deal with badly tempered stocks of bees ad given recent debate, thought it might be helpful for forumers to collect their observations in a fresh thread.
In the past I have found that colony temperament had greatly improved where a stock has been moved from a position of shade into full sun.
I have requeened bad tempered colonies with both virgin and mated queens and within minutes of inserting the Q release cage, there has been a very noticeable improvement in colony temperament (less following and reduced defensive behavior in the vicinity of the hive).
Two years ago I noticed that a colony had become very defensive, veil pinging 3m away from the hive. On checking them during a break between rain showers, I found they were nearly out of stores. When fed, their temperament returned to what it was previously, no defensive behavior on approaching the hive.
Weather conditions (particularly rain and thunder) can have an adverse impact upon colony temperament.