Note: All data correct as of April 15, 2018. The Test involving the ICC XI in 2005 is excluded.
We first look at the best averages in the fourth innings:
Boycott, Gavaskar and Hobbs top this table though there is very little difference between their averages.
We now look at those who scored the most centuries in the fourth innings (3 and above):
Younis Khan leads with 5 centuries, followed by Ponting, Gavaskar, GC Smith and Sarwan with 4. Bradman is also here with 3. Among current players, there is only Williamson with 3.
Now let see who disliked the fourth innings. These players made the most centuries (20 and above) without ever making one in the fourth innings:
SR Waugh (23), Mohammad Yousuf (24), SPD Smith and V Sehwag (23 each), IR Bell and MC Cowdrey (22 each), DC Boon (21) and G Kirsten (21). Of these only Smith may get a chance to change these figures.
Conversely, there are those who love batting in the fourth innings. Apart from Younis Khan and his companions at the top of the table, there are those who scored all their centuries in the fourth innings:
There are several who scored their only century in the 4th innings. The only current player is Shan Masood. And there is only one who scored his only 2 centuries in the 4th innings: W Watson (Eng) of the 1950s. Honourable mention to JB Stollmeyer (2 out his 4 centuries came in the fourth innings).
So we conclude that the 4th innings is indeed the most difficult innings to score in. Bowlers may have a different opinion.