Maybe not the toughest, because I didn't remember every draw of every Slam-Winner
, but a very, very tough Michael Stich had at his title win in Wimbledon '91.
R128 Dan Goldie (USA)
R64 Diego Nargiso (ITA)
R32 Omar Camporese (ITA)
R16 Alexander Volkov (RUS)
Q Jim Courier (USA)
S Stefan Edberg (SWE)
W Boris Becker (GER)
Goldie was a good grass court player, who reached the quaters two years before. Nargiso beat Mark Woodforde in 1st round anyway and Camporese was Top 30 at this time. So not that tough first rounds, but good adversaries to come into the tournament.
Volkov then was a very tough adversary. He was No. 25 in the world and reached for 2nd time in a row. He even served for the Match in fith set and was two points away from winnig against Stich, but the german came back.
And okay, grass was the weakest ground of Courier, but after all he should went to the final of Wimbledon two years later and had a very good run in Wimby '91 with beating Boetsch and Novacek in very straight sets in the rounds before losing to Stich. And of course he was No. 4 and won Roland Garros before.
Of course the draw was only that tough because of the last two opponents.
Edberg was Number One in the world and entered the final of Wimbledon in the last three years before. He was the defending champion and best grass court player at this time, winning all of his matches in straight sets like he did before when he won in Queen's until he lost no service game but the match against Stich.
And then the final, it was a huge national event in germany. Everybody sat in front of the television. It was the climax aof the german tennis elation. Boris, the national hero and everybody's darling, reached the final as expected. But not like in all of the three years before Edberg was the opponent of the three times Wimbledon champion there. It was his german compatriot Stich, he had to play in his "Wohnzimmer". Becker was the top favourite in this match, everybody expected him to win Wmby the fourth time. He was the emotional of both, Stich the highly reserved northern german, who reached his first GS-final. And from the beginning of the match it proceeded absolutely different than expected. Becker got more and more nervous, made a lot of errors and starts to swear more and more. Stich on the other hand played absolutely fine. It seemed so easy how he dominated Becker. Nobody couldn't believe. Even the umpire when he called after the last point: "Game, set, match Becker"...no, it was Stich...