League of Legends (LoL) Question: What are good instakill champs in ranked? (climbing from silver to gold)

I climbed as a Leona otp to where i am now. But i think Miss Fortune should be freelo :)

in my opinion fiora is best champiton to climb.

i guess Veigar is a decent oneshot champ? Annie too. oh, and LeBlanc of course.
but then again, it's not all about oneshotting everyone, eventually you will need to do more than just oneshotting everything or so. objectives, controlling, zoning, just to name a few mechanics are important, too. I dont play ranked so I dont know what gold is like, but I think you need to learn those mechanical things a bit too for the road to gold.