Which game do you think had the worst chaser ghost?
While I would put Sakuya on here simply for not being able to one hit kill you, I think I'd have to go with Ouse for the beach chase scene alone.
Not only do they have her have a completely glitched pattern (Having to walk instead of run to avoid running into her unless you get insanely lucky) but they also have her pop up in front of you no matter which direction you go in and she always disappears and reappears in that same spot whenever you try going round the opposite way. You literally cannot avoid getting hit by her unless you glitch the game and if you are playing without using the shop and have no Stone Mirrors...............
Just, an absolutely terrible flat out broken section of the game. They even have the gall to place a Shrine Maiden ghost there if you head down the left path who will more than likely grab you long enough for her to catch up to you. Worst section in the game by far.