Younis Khan's mental strength and the ability to deliver when it matters is unmatchable and he is an absolutely a big big match player.
When the team was 0-1 behind in a series against a strong Indian side in India, Younis Khan stood up like a warrior in the final test and played one of his career best ever performance in Bangalore and helped his team draw a test series in India 1-1.
When the team was drawn 1-1 against Sri Lanka in Sri Lanka in 2015, he again delivered a legendary inning of 171* chasing down total of 380 with ease on 5th day pitch of Sri Lanka, which led to his team winning a test series in Sri Lanka.
Again, during 2016 tour to England, when Khan was on his last leg and struggling and dancing all the way through the series, he showed an unbelievable resilience and mental strength just when it mattered, and as a result went on to put a 218 which helped put his team to a position from where he not only went on to win his team a match but also went on to draw the series against an in-form Joe Root's England.
Not long ago, when Pakistan cricket was going nowhere and was at a position when they could have lost a test match to Zimbabwe and even a series to them, he stood up and delivered a back-to-wall 200, which helped Pakistan from losing a test series to Zimbabwe of all team.
He was the biggest reason why Pakistan never lost a test series to some very high quality teams in UAE(the likes of SA, Eng, Aus, SL and NZ).
Even when he was young and a junior member to the likes of Inzamam and Yousuf, he didn't mind doing the harder job of batting at 3 at times and still went on to become Pakistan's leading run scorer in Australia tour in 2004 while Yousuf who was at peak scored lesser runs than Khan in that series.
His 149 at Auckland, 111 at Capetown or his 178 at Headingley proves his ability in alien conditions as well. While he was a little susceptible against high quality pace, but he knew how to find ways to score runs even in those conditions and that's what makes Younis Khan a legend of the game as far as test cricket is concerned and hence only behind Miandad among Pakistan players in purist's game.
He didn't had the luxury of Wasim, Imran, Waqar or even Akhtar, but the way he carried the Pakistan team is stuff of greats and that puts him as at least the best test batsmen among all his contemporaries and second best ever from Pakistan.