I know that Viktor already got some love from a previous patch, but...

...he just feels like he is underadvantaged. I just started playing him and I'm low elo, so my words aren't to be taken 100% seriously, but I absolutely love his kit and I can see him become a little better with some more attention. His winrate is amongst the weakest of the game, even though that he is a solid pick in high elos. I believe that this comes from the fact that he barely gained profit from the mage item changes (unlike and or people who can rush Ludens first item). Mages who were gated by mana early barely has this problem anymore and can achieve some solid burst. Viktor, on the other hand, is both gated by mana and the fact that he can't rush proper items that are now "must have" in early game for 90% of the other mages. Yes, and , his core items, gives mana. True. But he must go all the way through these items to barely have some backup mana while someone else can just buy or and have as much mana if not more. The problems that is confronted to are definitely caused by his item gating. You can see the link between the fact that the mage with the most item gating is amongst the weakest and the fact that the mage with the LEAST item gating is the one with the highest winrate in the game as of now . I don't believe that Viktor needs THAT much changes, or else he'll just become straight out OP in high elos (maybe...), but I'll still enumerate a list of changes that I personally believe would be good for him if applied separately:

1- Make him able to cast every single spell from his kit while still moving. He can already do this with his laser and this is a key part of his kit since he is made to be mobile while casting his spells. Making so that his Q (on cast, not on the auto-attack part) , W and R could be cast while moving could be a good benefit, without being game breaking.

2- Make so that his Q refunds mana on unit kill on both of his part. Adding some cooldown reduction on either part of it could be good too, considering that many mages as some sort of this aspect as well.

3- give an actual enhancement to his ult. I could see something like "each damage wave that touches an enemy champion enhances its speed, excluding the initial cast damage". Prior to its evolution, the ult basically does nothing outside of its initial damage so 80% of its damage is actually lost, unless you actually stun someone with your W, who doesn't do much against someone who knows/can play around it

4- Change how you can upgrade your Hexcore. It would be ok if this item could be upgraded without having to use gold, even if it takes an inventory slot. Giving the opportunity to focus on your first item instead of having to upgrade this item for the first 2-3-4 times you recall could be so much game changing. Making it upgrade with goals like "X spells cast" or "X executed minions" or even "X collected samples" in a similar manner to Bard's passive, would feel so much better and would actually go well with his lore

I don't claim having the best logic considering his kit, but with one or two of those changes, Viktor would actually become a mage on the same level as the others.