I just really hate how much of a snowball Irelia can be.
Her Q later on can one shot ranged minions, offering her instant healing and good gold with a minimal expense of time since it resets on kill and at that with a low mana cost.
Irelia's W can be tricky, although a good tool, not something I'd call broken. Let's leave it at that.
Her E can be good. It's an easy read as long as she doesn't hide it with her other animations and flashy moves, getting hit by it is pretty punishing because it prepares her passive on you rather easily.
Let's chat about that passive. Ionian Fervor is pretty damn solid. Once you hit max stacks, you do up to 68 + (16% Bonus AD) magic damage , up to 50% attack speed at max level, and absolutely shreds through shields (up to 136 + (32% Bonus AD) magic damage).
Now that R, the ultimate, something that's really annoying and that can turn the team fight entirely. It knocks away enemy champions, slows them for 60% (pretty big slow if you ask me) AND disarms the one's hit by the ability. Now the damage isn't really surprising, nothing too much.
It's the fact that it disarms you for 1.5 seconds, making you absolutely vulnerable that annoys me. After you're hit (It has a generous hit box), Irelia can dash you, CC you with her E, dash you again and if you retaliate, you get hit with her defensive option. It technically means that you can't escape her so that she can dive the ones hit without repercussion. It also procs her Ionian fervor too.
Honestly, the champ is pretty slippery, making it hard to trickshot sometimes as a good defensive and hard CC as well as great fast and easy damage. If you want to counter Irelia, you'd have to outrange her and stay back quite a bit as well as minimise her farming capability so she doesn't snowball too hard...
Oh..
...