I could name 3 champions for this kind of thread. Hopefully my answers solve your questions:
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I hate dying to his death mark as much as the next guy, but he is probably one of the fairest assassins in the game. He has clear windows of opportunity to punish like his W being on a long cooldown and when he pops it but his other skills don't connect, it gives the enemy the window to hurt him. He has a much more limited range than most assassins and that when he hits his combo, it sure can hurt a lot and rewards the Zed player of the opportunity of going in for the kill or making the enemy laner retreat so that he can get CS. He's also over-reliant on his ult to kill people so if his ult is down, his kill and outplay potential is drastically lowered. Overall, Zed's kit is healthy and shows good skill expression if he's played right.
I don't want to remember pre-assassin rework Zed though. Pre-assassin rework Zed was very consistent, could win any match up very easily and that since his W provided him more AD off of his bonus AD, getting a BT on him means you can literally kill anything in sight, even tanks. Zed used to be one of my power picks when I couldn't play Yasuo for any reason but ever since the assassin rework, I rarely play him nowadays.
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Overall, Ezreal's pretty balanced in that his kit is all skillshot and that his reliable escape or engage (which is his E) has a fairly long cooldown. Despite his large safety net for an ADC, he's much harder to use than the other ADC's as he's much squishier than most ADC's, he's all skillshot; requiring you to aim pretty well on his skills and that he's pretty feast-or-famine in that he lives for the mid game and if he doesn't get strong in his strongest point of the game, he's gonna fall off pretty hard. He's also snowball-reliant for a safe champion.
But other than that, his damage overall aren't pretty insane, but pack a punch if played right. He also doesn't suffer the "Snowball Syndrome" where X champion gets borderline broken with just 1-2 items like most other champions. Even though his quota is Manamune/Muramana and some other Sheen deriative, getting those 2 makes him strong, but still manageable to play against. Overall, he's an ADC with a fairly unique kit with defined strengths that aren't very easy to abuse on, and weaknesses that aren't very easy to punish. His mixed damage is nothing to scoff at though. However, he could use some tweaks to his numbers as he's a bit too lackluster in the meta imo.
The only times Ezreal was pretty insane though was when items like Spirit of the Elder Lizard, Runeglaive and release Iceborn were in the game.
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Yes I know, this is a controversial point in a thread like this but hear me out. Yasuo's kit is overtuned yes, but is fairly healthy to play against. If you look into his kit deeply, you can see that if you look into his skills individually, they're very lackluster but when his skills are combined together, it creates a kit where every every ability blends well with the other much more than other champions. Majority of his damage is also budgeted into his double crit passive which means if he doesn't get his crit items, he's not gonna get any damage as well. Because of his kit having naturally high damage and mobility, it's offset by the fact that he's very squishy and that catching him out with any CC can severely punish him. Even the simplest slow can screw him over if he doesn't have his W or E to back him up. His passive shield is what also gives him weaker survivability as it's very easy to pop, but manageable if the Yasuo player can time the shield right.
Also, he has fairly low base damage in all of his skills, barring his R as most of his power is placed into his passive. His R is powerful yes, but can only be activated through any source of a knock-up, which is fairly occasional unless the Yasuo has other friendly knock-ups with him. Overall, all of his abilities are situationally strong in that; his Q is only strong when you get your items and that it has a knock-up, his W is only powerful against projectiles and is easy to walk over, his E is only strong when he has things to dash to (like the minions) and his R's only strong when there's a knock up for him he can capitalize on. His kit's power fantasy which is the, "Agile Swordsman than can cut through everything but dies pretty fast himself" is fulfilled and executed pretty well. I main Yasuo so I deeply know his in's-and-out's and his limitations as a heavily overloaded champion.
However, release Yasuo and Frozen Force/Tank Yasuo was a nightmare to face against. I've tried both and yeah, Yasuo's broken beyond relief during those times.
Edit: What's with the downvotes? Is it because I mentioned really flashy champs and not basic ones?