I' gonna have to go with oblivion on this one. Not terribly scary, but I remember my first Land drough fight.
I entered the cave, and with my Battle hunter gauntlets with life detect in 60ft, I took a look around to see what was awaiting slaughter. A couple mud crabs, sure. A few daedroths, not looking forward to those. A ghost or two, goo thing I brought my sunfire sword. And a...await, what the hell is that shape? It's freakin HUGE! It looks o be....human? No, it seems to have crab leg. Well, maybe it's just 2 enemies standing next to each other.
2 minutes later.
Immergesfrom water.
"ahh, that was a refreshing swim. Now those two enemies should be aroun.....oh. my. god. RUNAWAY!
( I did finally work up the courage to kill it, but still, finding enemies you don't know how to kill on hard mode is not a good thing.)