Question for the design and balance teams: Who are the most/least successfully designed champions?

I'm not asking you to call out a fellow RIOTer, of course, for poor execution, because, after all, it's a team job, and something that looked good at first might have turned out unexpectedly.

I would like to say that I was looking at a "whole package" view as well. And, while my view isn't that of a RIOTer, I'd like to provide examples of what I am talking about.

I think a really WELL designed champion is Morgana. Her theme is excellent; she looks like a corrupted champion, and she plays like one with a spell-casting kit filled with disables and damage over time. Not only is her design cohesive with her kit, but her kit is cohesive with itself and is a paragon for counter-play in league. Her Q is a long-range, blockable, single-target skill-shot, but the reward for landing it is nice damage and a long-duration root. Her W is a nice AoE DoT, but it isn't "free" damage unless you can land a Q first. Her E excellently counters certain enemy abilities if used well, but it can also be countered itself by waiting it out, switching targets or simply bursting through it, and her ultimate has a very heavy potential payoff but it can be walked out of and has many synergies and antisynergies that make it a rich ability that adds a lot to team fights.

In contrast, Irelia is a really poorly executed champion who LOOKS like a telekenetic, ranged blade wielder but ends up being a rather build-agnostic generic beefy brawler with built in sustain, true damage and a large duration targeted stun. In addition to her kit not really being cohesive with her image, it offers very little counter-play which has made her a perennial competitive pick despite very little "special" gameplay contribution.

Of course there's a slew of champions in-between like Tahm Kench who completely lacks counterplay when fighting a fragile melee champion, but whose design is overall cohesive. Or Evelynn who's actually relatively balanced, but, inexplicably tends to build as a beefy brawler despite her design seeming to indicate that she's a fragile assassin.

Anyway, I framed this question to RIOTers, but anyone can feel free to add their 2 cents.