Steinitz, Euwe, Alekhine,Keres and Nimzowich might have been in the list as well. Jan Timman has played some memorable endgames. In fact there are hardly any topplayers past or present who dont have impressive endgame skills.
But in the end I voted for Em. Lasker (assuming that Lasker dit not stand for Eduard Lasker).
If only for the impression that the endgame Em.Lasker-Ed.Lasker made where the former held a draw by escaping in a drawn N vs. R+p endgame. Em.Lasker also published several endgame studies.
Korchnoi has gotten very few votes compared to Karpov, which is interesting. Bent Larsen wrote prior to the 1978 match he considered Korchnoi the stronger endgame play. Which was more or less confirmed in the match.
Everyone in the list has shown us some wonderful endgames, so choosing the best is essential impossible.
And I cant argue or find fold with those who voted differently.
One further mark: some posts argue that X or Y really cant be the best because he made an error/lost some endgames.
But I can recall famous endgame losses from almost everyone in the list... Chess endgames can be deceptively difficult
Actually I closed my vote after picking Lasker (it didnt register I has five).
Four more of my favourites in random order:
Nimzowich, Botwinnik, Smyslov, Korchnoi.