You already know the answer to your question. Pick something and ask about it specifically. For FK H10, Gnut is MVP of course. But Criodan is surprisingly good, considering he's an epic. Slightly lower chance of landing the freeze than Yakarl, but an extra hit is very useful. Phantom Touch is also very strong for FK H10 since you get an extra shield hit with it.

Arix solo spider10 hard

actually i dont .. gnut , 2 of them .. isnt working for fk hard 10 .. only up to 4-5 ... 

For city .. i havent played it enough to know champs that been extra useful to clear certain stages ... 

I dont have any issue with spider hard 10 , dragon hard 10 or IG hard 10 :P just FK hard 6-10

Should be quite easy with that team. I'm sure there are better options, but Gnut x2 + Yakarl + Fatman x2 should do it very easily.

2 cardiel , 2 gnut and yakarl doesnt work so it a stat issue .. what about city ? any champs worth booking and masteries in those ?

For Cursed City especially, the answer is never "book this random champ just in case". If you have a room that you need someone specific for, then level and book them. It's that simple.

As for FK H10 - stats shouldn't be hard at all with those champs. I doubt you even need more than around 250 SPD to pull that team off. Not sure what is stopping you.