Cho+Stoneplate one-shots are actually rare and incredibly situational.

Getting something out of the way here, my definition of one-shot is 1 instance of damage bringing a champion from 100% health to 0%. Examples include full AD Darius W crit, old Nasus' Q crits, and full AP Pantheon dead-center ult.

Using that definition, one-shots are very rare in League and usually only in full damage builds.

So, Cho'gath. The big monster thing itself can and always has been able to one-shot via the full AP build as the scaling was just good enough to reach 1.2k true damage while a Luden's proc would deal about 200. What is new is the fact that the other builds can achieve this one-shot.

For the sake of easier calculations and for a more common scenario, I'm ignoring HP runes and cinderhulk as Cho'gath is primarily a top laner. The winrate in the jungle is caused by the mains.

In order for Cho to get the one-shot in the tank build as that is one with the most health, he'll need to reach 6.5k HP so that stoneplate puts him over 13k. Cho'gath reaches 2k health at level 18 and enter late game with atleast 10 stacks on the average game, so 1.6k health+base=3.6k. He needs stoneplate it even accomplish this and I doubt one would forgo boots, so 2 item slots don't go to health. Cho starts RoA as it solves a lot of his problems, so that's 500 health and 50 more damage on ult due to AP scaling. 4.1K. This IS Cho'gath so getting close to enemies is problematic thus he'll be getting a RG. 4.4k. He's gonna get Warmogs for the major health boost. 5.2k and one item slot left. Yeah Cho isn't reaching the threshold unless he either: A) Gets like 3 more stacks B) Sacrifices boots to get an item that provides 500 health and gets another Warmogs or a Frozen Mallet C) Gets HP runes so that he can get a Deadman's Plate instead of something that provides 500 health. And he also needs to be near 3 enemies for the doubled health and if he really wants the juicy one-shot he can't get Protobelt as that'd hurt the enemy preventing a true one-shot. AND THIS IS LATE-GAME! You know, the thing that supposedly rarely happens? And is also Cho'gath strongest point in the game due to his nature as a void champion?

For this to happen outside of late-game Cho needs to get really ahead and by then you're donezo. And I mean 17 stacks at 27 minutes ahead.

"B-but what about the burst that out-damages assassins???" Bitch Cho'gath has done that for almost his entire existence in every build because his base damage is off the charts. 750 base on ult at level 16. The only reason you'd be complaining about it now is that he's actually popular rn.