Dark Emperor Katarn vs. Luke Skywalker
In Jedi Knight, the player has the option of turning to the Dark Side and ending the game with Kyle Katarn as the Emperor of the Empire, as of 5 ABY, empowered by the Valley of the Jedi.
Surely Luke would probably flip and want to take him out.
So, the battle takes place in Kyle's Throne Room.
It is a contest of lightsaber skill and Force power.