Has there been anyone with one yet?
What’s a legendary? You mean a 4*? If so, there are lots of people that have them maxed.
Heh. You’ll see maxed level 4****s on hacked teams all the time.
To answer your original question, there are people with high level ones, but overall you’re better off spending your iso on the 3***s as they’re better balanced characters.
People level up what they’re playing. The Legendarys (4****s) are not worth levelling atm.
Unless you got your money by stealing, it simply doesn’t make much sense to invest heavily into the 4* until you have a significant number of characters at level 100+.