Football managers have to have that bit of fierceness about them when dealing with egotistical players who may or may not respect their authority.
That intensity and passion is at times necessary to get the best out of some players too. Sometimes, though, it is not such a good thing.
Being fierce can mean, among other things, being hostile, passionate or intense. Some of these managers have all three and others not so much.
The managers on this list have had fierce responses to their own players, the game officials, other coaches and the media.
Here are some of the fiercest managers in World Football.