"I mean come on the guy is almost impossible to kill like fizz"
If you think Viktor is hard to kill (given that while Gravity Field is EXTREMELY powerful as a zoning or lockdown tool, its easily escaped by any dash or blink), I'd hate to see you fight truly safe mids like Xerath, Lux, Ziggs; or people you literally CAN'T kill alone (well, most of the time) like Malzahar.
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Nah, I don't think there is really any reason to nerf him. His CC requires you to stand on something for too long, and his damage is fairly normal for a mage.
Viktor's burst is actually pretty up there (I don't think its quite THE highest, but I believe on paper its within the top 5), that said there's nothing wrong with that, given that he's balanced by having no mobility, a very powerful but situational stun and one of the most awkward skillshots in the entire game (made even WORSE when you're trying to use it at close range).