I don't understand why people keep saying assassins are weak and can't kill anything...

I mean can kill squishies in just one or two autos.

Like Tristana is the perfect assassin, just jump in, throw your execute on top of any squishy or troll champ like and auto with your and they die right away, and for slightly tankier ones like with maybe you need to auto like two more times but your will do all the work anyway.

And Vayne with can just R+Q auto any squishy like and kill them in one hit

Twitch is the same as Vayne but he actually shreds the whole team instead. If they have an extremely tanky champion, like with and his jungler's he might need to press E as well but that's ok.

Draven isn't exactly an assassin, more like a burst tank, but his Q auto+auto combo can one shot squishies like so he counts

And Jhin is a bit different because sometimes he builds weird items like which I think are outdated items from when assassins built lethality instead of shiv, but his +auto combo can insta delete even the tankiest champions, like the afore mentioned