A very famous and well-used catchphrase is ***greatest of all time***. 

Sometimes an extra word is put in, between _greatest_ and _of_. For example:

* Greatest [**swimmer**][1] of all time
* Greatest [**Olympian**][2] of all time
* Greatest [**athlete**][3] of all time


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By the way, I'm not claiming the Phelps is any of those things; I'm just showing how the phrase can be used.

  [1]: http://www.thedailybeast.com/articles/2016/08/09/is-michael-phelps-the-greatest-swimmer-of-all-time.html
  [2]: http://www.teamusa.org/News/2016/August/10/Now-And-Forever-Michael-Phelps-Has-Become-The-Greatest-Olympian-Of-All-Time
  [3]: https://www.theodysseyonline.com/phelps-greatest-athlete-time