The game below is from the Honinbo preliminary league. Black resigns after only 76 moves, despite there being no super complicated fighting.

So... where did Black go wrong? He got very little benefit from starting the ko in the lower right. But could he have been in a disadvantageous position before that?

Well, and the following sequence in that corner looked kinda rubbish to me (white got a tenuki out of it and still got a nice shape, whilst ended up overconcentrated). And then with the trades on the lower side white called black's bluff a few times and did fine out of it.

There's a ladder. Suppose at O4, White at O2, Black takes in the "ko", White at P1. Black shouldn't connect. Therefore Black will have to grovel.

Edit Not a ladder, indeed, as has been pointed out. But White can take a tough line in the ko.

Can't see the ladder