I defeated a level 52 player and I did't get the achievement.
Anyone could explain why ?

look at other ppl's achievements, it ends at lvl 51

Oh! Ok. Thx

So this means that defeating a level 52 or plus player isn't worth an achievement?! I find it weird ..

Fizzer probably just hadn't implemented achievements for players that high yet.. not expected people to falsely inflate their ranks with lottery games, or for people to play enough games to already be to that level.

most fo the players over that lvl have only inflated their points at the ebggining, ladder games and multi-day games and tournament games give enough poitns for you to rise fasr

Achievements are designed so that players could, if they want to, try to get every achievement. Levels, on the other hand, go to infinity. Therefore, the defeat achievements have to stop at some point.

But you yourself can't get all of them. (defeat the player that invited you to warlight)