1. Quan Chi (sky drop can severely screw up your spacing, shuts down full screen zoning and runaway tactics as well as jump ins and you can do it on reaction, mix up's coming out of his ass, 3/4 of the screen trance that hits you jumping and ducking, good uppercut, fast fireball and of course that unblockable damage is a pain in the ass in a close match)
2. Baraka (very few people I've fought play him well but the ones that do are scary with him)
3. Sektor (all around solid character with no real obvious downside except he just doesn't have any super cheap tactics like the top 5)
4. Liu Kang (so many mix ups, good zoning, I haven't seen another character that can start a combo off of so many of their random moves)
5. Raiden (although he may not beat the best characters in the game easily, he can demolish a good portion of the cast just by playing mind games with those teleports, Bwizz koth video was pretty crazy)