What is the best achievement of Federer's ATM?

[fed2004-2017]

5 AO
1 FO
7 W
5 USO
302 WEEKS AS NO.1
237 CONSECUTIVE WEEKS AS NO.1
87 WINS AT AO
84 WINS AT W
18 SLAMS
10 FINALS LOSSES
WIN A SLAM AT 35 YEARS OLD
RECLAIM NO.1 AT AGE OF 30
HAVE A 14-1 GS FINALS RECORD AGAINST EVERYONE ELSE BESIDES NOVAK AND RAFA
HAS A 4-9 WIN LOSS RECORD V RAFA AND NOVAK COMBINED

 

[metsman]

Winning 8 of 10 grand slams, losing the final of the other 2 to probably the greatest single surface player at his peak. That always will be it.

That and his performance against the top 10 in 2004 will always be imo the most impressive Federer accomplishments.