Ahahaha I love these meta sheeps right?
A week ago, I bet this guy was one of those "Aatrox/Urgot needs huge nerfs" board posters. If we told him that pick Viktor top then he would say the same shit as now :D.
But then Viktor is picked top (and btw he is not even doing very well) suddenly Viktor top is broken, in 1 day champion.gg has not only enough data for this pick to show winrate but also says he has insanely huge pickrate and also number of games played - this just means that all sheeps just started OTPing Viktor top and now we have "Viktor top is broken and needs nerf" boards posters and when you say them pick this champion they say you can't because it wasn't played at worlds.
Anyway, I can confirm that assassins and divers are or rather should be counter to toplane IBG Viktor. Especially AP assassins like LB, Akali should work extremely well because the average Viktor top meta sheep player will play Klepto and rush IBG every single game. IBG is really powerful item in lane against AD but won't give much besides 20% cdr against AP. But even AD assassins and divers should work well because the main reason Viktor is so lane dominant is his spammable shield and continuous damage. But if you jump on him and burst him hard he won't be able to return the trade as he will be too low to do that safely (if he won't be dead already...).
Obviously if someone pick Camille, engages with hookshot and misses the stun, then he will not only lose the trade but will also eat the return damage on disengage... Doesn't mean Camille does not work against him though. Basically every strong 1v1 duelist and splitpusher will work. Even when Viktor will have advantage early, 3 items and he won't be able to stay in lane.