First off, I don't know why it has to be a hundred. Plenty of sub hundred knocks in the 90s, even sometimes 80s clearly classify as match-winning.
Still, I'll give it a go with Imran, when I get the time.
When bagapath was conducting his all -rounder ratings, he specifically said to some consensus that it's the 100's that separates the batsmen who can bat from the all rounders. And it's easier to pin point the signature innings....
And I can save you some time.
6 hundreds.
1. Vs Australia, 3rd innings hundred where he and Wasim likely saved the game and set up a draw. Definitely a plus and his most. Impactful innings. Draw
2. Vs England, 1st innings hundred in score of 708 where his was the 3rd hundred of the innings. Draw
3. Vs West Indies, 1st innings hundred that set up competitive score. Impactful score. Draw
4. Vs India, 1st innings hundred in total of 652, where his was the 4th hundred of the innings. He gets credit for wining this game with the ball though. Win (probably best came of career)
5. Vs India, 1st innings hundred in total of 487, 3rd significant score of innings. Draw
6. Vs India, 1st innings hundred and top score in competitive innings. Draw
6 hundreds, great. 0 4th innings hundreds, 0 match winning innings, only one even came in a (10 wicket) victory. To his credit he did have 1 stabilizing and potentially 3rd innings match saving knock.
As you mentioned it, I also looked into the 90's and 80's and there was none of those either. There was a 1st innings knock of 93 vs SL in a draw however.