I enjoy playing ad carry a lot, but I often have a problem : nocturne ( and other gap closer champs...). I try to deal some damage but nocturne jumps on me (of course, its his job).

Here is what I tried

Fight him : I usually lose the fight because I am squishy and he has a fear

Buy a guardian angel : Works once, but I die right after

Mercurial scimitar : Seems like the best option so far, but when nocturne is not alone they still manage to kill me

My question : is there any other ways to counter hyper-focusing champions.
I do not like blaming it on my team, but maybe its their job to keep him away from me?

It's nocturn...you are an adc. There is nothing you can do but flash away in my opinion. Junglers are meant to kill squishy types, it's their job. I mean, unless you are super fed you shouldn't be able to kill the jungler in a 1v1.

I'm aware of that, I just wanted to know if there was any other options , thank you for answering

Having a champion who can kite him is almost an essential when playing against Nocturne, or Twisted Fate, along the same vein. If you're staying behind your tanks, then Nocturne will have to go past them to get you, and then he's over-extended. If you have someone like Maokai, Blitzcrank, or anyone who can kite on your team, they can throw him off of you pretty easily, or slow him down.

Just stay with your team when you're fighting against him, and he shouldn't be a big problem.

If your team is not being helpful, the only thing you can really do is try and flash away and then kite him. Ashe can kite him all day with her slows and ultimate, and Ezreal has Arcane Shift that he can use before you get hit by a fear. At the end of the day, you can't say you didn't try.

Another thing your team could try is to jump on the enemy ad carry and the other squishies on the team. A Skarner ultimate or a giant tree put right on the enemy ad carry will prevent them from being useful, either. Even if you do die, then they have lost almost as much as they have gained.

Thanks a lot, your answer was helpful!

Your team needs to be peeling for you, you need to position yourself where Noc is in a bad spot if he dives on to you (behind front line, but not so far that they cannot help you).