Magnus Carlsen is world champion. other grand-masters are not.
What is one thing that differentiates Magnus Carlsen from other grand masters?

It's just the same as an A-player vs a B-player.

Magnus memorised "houdinis" winning lines in all the openings.
Hes a human chessengine , play magnus age 21

"There is an equal position on the board, and the opponent thinks: this is dead drawn. I can play almost anything and there is nothing he can do. But Magnus plays on, seeking complications, setting up threats. He is narrowing the margin required to hold the draw. Soon his opponent is thinking: why is he still playing – I can hold a draw with any of these three moves. Then: I can hold with this move and with this move. And then: I still have one clear way to hold a draw. And under the strain of constantly having to solve deep and complex problems, more often than not the opponent will crack. Magnus wins not because it was in the position, he wins because he is Magnus."
That sounds more like 2200 vs 1800 who doesn't know any better.
I'm pretty sure pros take the endgame seriously even if it's objectively equal.

"There is an equal position on the board, and the opponent thinks: this is dead drawn. I can play almost anything and there is nothing he can do. But Magnus plays on, seeking complications, setting up threats. He is narrowing the margin required to hold the draw. Soon his opponent is thinking: why is he still playing – I can hold a draw with any of these three moves. Then: I can hold with this move and with this move. And then: I still have one clear way to hold a draw. And under the strain of constantly having to solve deep and complex problems, more often than not the opponent will crack. Magnus wins not because it was in the position, he wins because he is Magnus."

Hes obviously Morphys reincarnation.
Hes also why I hate being a natural player , in my opinion he memorised "houdinis" winning lines. probably all of em.

Carlsen memorized Houdinis lines but do not play those lines. That what makes him WC and highest rated player.

What is one thing that differentiates Magnus Carlsen from other grand masters?