Kindred used to be a lot stronger, but Riot had gotten naughty, stole them away in a van, brought them to a basement, did some things, and just flat out ruined the champion.
Before the 7.11 Rework, Kindred had a weak early game, but her passive gave her a lot of early game pressure that allowed her to scale really well. You could do well in the beginning and be a monster by mid game. Or you can do ok and scale towards the late game.
Afterwards, they normalized her into an ADC with some really inefficient item dependencies for her role. She has a much weaker early game, applies no pressure. And has a late game that is basically a normal ADC. It's very underwhelming and unrewarding to me for the shit you need to put up with.
I can see why they tried to push her passive's power into her abilities. It makes them more meaningful. But overall they are not powerful enough.
Her Q is gives an attack speed steroid. Which would be nice if she still had on-hit damage linked to her auto attacks. Otherwise this is only a miniscule boost in DPS. I'd rather have Q empower her next few attacks based on the number of marks she has.
Her W is where her onhit damage went. But it's too easily avoided. Can only hit one target. And it's fucking impossible to maximize the usefulness of this ability outside of refreshing your Q. Sure with enough marks, wolf can put out some hurting. but it's .5% per mark. 12-13 marks is where you're doing awesome as kindred, and that only gives you %6 current health damage on an ability that is easy to run away from. To make matters worse, the damage can not be maximized very well because wolf applies no form of CC, and attacks at half of Lamb's attack speed.
E grinds my gears massively. It is her only form of CC in her kit. And it is tied to an 'execution'. Except, this execution isn't really an exectuion. It just does more damage depending on how low your enemy is and where your threshold is. That threshold being determined by crit chance... which forced Kindred into building some of the most fucking expensive items on the second worst income. The power her passive gives to this ability is a little more respectable... but it is still too low in my opinion.
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If you want to learn how to play Kindred... honestly you have to be significantly better than your opposing team. And you need to be a little more sneaky. Try watching some of RedKind's videos on youtube. You also have the Kindred Main's reddit.