To get Leon on Brawl Stars, you can only follow one path: open boxes, lots of boxes, lots and lots of boxes. You may think that this is an exaggeration, but you must keep in mind that we are talking about a legendary brawler.
Is it a big deal that he is a legendary character? Actually, yes. The probability of a legendary brawler appearing in a normal Brawl Box is 0.1296%, and think that in Big Boxes, the percentage is tripled (and in Mega boxes, it is multiplied by 10 in comparison to the normal box).
What does this mean? So, either you spend money, buy gems, and exchange them for Big Boxes or Mega boxes, or try to complete the seasonal rewards (with the Brawl Pass activated you have more possibilities, which also means spending real money) to unlock these special characters.
In the past, Brawl Stars had a lucky system in place, where if you did not unlock a new brawler in one box, your chances of getting the next one increased. Now, it no longer works that way, and the odds are the same for everyone.
Leon is one of the most wanted characters because of his enormous offensive capacity, his great speed, and his special ability, which lets him hide on the stage and run away from dangerous situations. For quite some time, he sat on the throne as the best character in Brawl Stars, with all that that entails.