I hate what they did to Hungary the most in this game, in F1:CE it was one of my favourites but they really screwed it up for this. Several corners that were fun but difficult have now just been made difficult without the fun part. Specifically the last two corners and especially turn 6, which used to be flat if you were daring in CE.
I actually enjoy Singapore despite its strange rhythm and Valencia is a blast to drive. I'd probably say that turn 15 at Hungary is my hardest corner in the game because it has no grip whatsoever. You carry slightly too much speed, you run wide, you carry slightly too little speed, you spin. Its almost impossible for me to be consistent at this corner, whereas all the afforementioned corners I enjoy the challenge of and are quite easy if you work out and practice your approach and lines.
For example, turn 1/2 at Turkey and Brazil are easy if you practice, they may seem bizarre and difficult at first because they are effectively blind, but if you practice them enough and make notes of gears/speed/braking points you should be able to build some confidence and its easy then.
Corners like Tabac require more concentration, you have to make sure you don't go wild on the throttle or you can spin or tap the wall very easily. Even with practice corners like this are difficult but time and experience makes it a bit easier to deal with.
Corners I absolutely love are turn 5 at Abu Dhabi, turn 4 at Korea, Casio at Suzuka, Nouvelle chicane at Monaco, turn 3 at Bahrain, etc. Proper ballsy braking corners where you can brake really late and get the drop on people. I just love out-braking people so massively like that. Braking at 100 metres at turn 5 Abu Dhabi is an awesome thrill because you almost don't make it.