There are so many counters to Darius right now it makes my head spin.
You have 3 ways to beat Darius. You can outrange him, outdamage him, or survive him.
Jayce, Kayle, Kennen, and Elise all beat him. You have to be a little careful on Kayle and Jayce though.
Volibear, Olaf(This is a really close one), and Renekton will all beat him in fights for the first 10ish minutes of the game, which is when he's most threatening.
Not very many champions sport the kind of sustain you need to survive Darius. Notable choices include Cho'Gath, Nasus (You need lifesteal quints and armor reds/yellows to get away with this on the doggie, and you must be mindful of ganks), and Udyr.
However, the most important thing to do against Darius is not eat his Qs. Most Darius' are not good at the game (Because most people aren't good at the game, myself included), and will use Q as harass and wave clear. No, that is wrong. Darius is best when he can use all of his skills at once to stack his passive, then chase his opponent all the way to their tower. If you notice him use his Q to farm, that's your chance to either make a play on him, or farm safely.(You have to farm even when he has it up, but you can at least feel better about getting close to him with his Q down).
Darius is what bad top laners use to beat other bad top laners, because of how simple his kit is. If you understand how to exploit his weaknesses, and are mindful of his strengths, he's not a scary laner at all.