Online endgame masters

Take your time and make heavy use of the Analysis board.  That alone will improve your results dramatically!

Beyond that, start thinking in the middle game about where you want the endgame to go.  For example, if you have a choice between losing a pawn where the enemy king is castled or losing a pawn on the other side of the board, which one will result in a better end game?  Can you make the far pawn a passer and score?  If you start thinking about the endgame earlier, it will improve your chess.

Last advice - study endgame theory!  I have beaten many opponents because I knew a little more theory than they did.  Best of luck.

Yes, in the endgame you can not only refer to endgame references but you can also calculate out long sequences of forcing moves, which becomes even easier with the analysis board. If you find that players of equal skill in other phases of the game seem stronger in the endgame, that might indicate an endgame weakness in your own play, or else it might be that you just need to be more patient in that phase of the game, since your intuition can lead you astray a lot of the time in certain types of endgames.

"No mistakes" and "the perfect move every time"...I wonder if the OP is suspicious of engine use?