Two champs i am talking about..and actually amazed arent talked more about are Nasus and Shyvana. They are both, in my opinion, extremely unhealthy to play against.
Primary issue i have, is the sheer damage. Many late game scalling champions, Nasus included, had a strictly designed line how they operate : From nothing - to average- to monster....it is a fair trade off with a DISTINCT weakness which is easily exploited. That made it, very logical- u have a decent timeframe in which you can operate to shut them down, or slow them enough.
Tweaking the numbers..as Riot loves to do, and adding constant band aid to champions (Vayne), so they can, you know..always offer something- actually ends up creating a abomination to deal with.
Shyvana falls into same category..tho in her case, additional issue is the..how do i put it- very cheap way in which she can do alot. Her rage builds too fast, her clear was never tampered with, dragon form E has..pretty much idiotic damage. Further issue is, both ap and on hit are equally busted and viable, with zero actual drawbacks.
Second issue, albeit minor is of course the playstyle.
The famous "ill run and shove myself into you , and you cannot do a thing about it" aka Udyr style..is simply exceptionaly frustrating to deal with. The "book" answer, "simply" cc them and kite them away..let us be completely honest - is bullshit. Time and space both of these champions create with their kits and body alone even versus a decently organized soloq team, are too much.
I would be happy to hear opinions from others as well on this