Little spin on things, what's the most difficult plains game you've hunted?

I'm pretty much a spot/stalk only, but have sat in some make shift blinds while in SA. 2x to the Limpopo area, both of which differed quite a bit from one place to the next and once to the Eastern Cape. Much more challenging hunt(s) for the most part in the Eastern Cape for those who haven't been.

1st time over there, took some effort to get a decent opportunity at a Gemsbuck. 2nd time put on a few miles chasing after Zebra's and attempted hunting duiker or steenbok, but didn't have any luck. Took a really nice steenbuck this last time and would still like a nice duiker.

Going back in '25 for a cow cape buffalo, but looking for other animals that on average are more difficult to hunt vs others. Going back to the 1st place I ever hunted over there and it's for the most part pretty flat and very thick.