Explain yourself, there isn't a single ap carry on which that is bad.
Yes, but there's also only a handful of ap carries on which it is good.
It's stupid on Viktor. Viktor is a burst caster that's meant to take people down from 100 to 0 in a combo. You completely waste the %hp passive by nuking shit, and you waste it even more given how your only CC to trigger the full damage from lazer poke is the gravity well, which is unreliable to say the least. So the only things left are some pathetic bonus hp, seriously low bonus AP and some mpen, all of which gets outclassed by any big item that builds from a large rod. Furthermore, given how Vik is gimped by the hex core, AND his ranges are utter shite, which means you absolutely MUST build boots/rabadon/2x tanky ap (usually rylai + zhonya) and finish up either with void staff if there's lotsa mr or abyssal. Laundry Torment makes no sense whatsoever on Viktor, and you should never get it.
Which brings me to my next point - it's a horrible and overrated item that does fuck all and is only seemingly good on paper. It gives pathetic bonus AP compared to other big items. It gives shit bonus HP compared to RoA or Rylai's. The mpen is relevant only for like the first 15 minutes of the game when you have a guise. The passive %hp damage is not only unreliable (needs cc to trigger full damage), but also crap (a
dot doing
current 2-4%hp is for the most part trash), and usually counterintuitive - when
exactly do you use it? Only poke-oriented champs really profit from it, and there's not exactly a lot of them out there.
I've been thinking very hard who can actually use laundry torment to its full potential, and in the end I can only name 2, and that's Vlad and Cassiopeia. If you are getting it on other champs, in 99% cases you are a horrible person and you should feel bad.