The best champions outside of lane to counter Viktor include Zeri, Aphelios, and Kalista. These are all great at countering Viktor with high win rates over 54%. Even if these Viktor counter picks are not chosen in the same position as you, it's not smart to play him into one of these matchups. They will very likely win against Viktor.
Yet, if the enemy team choses either Amumu or Tahm Kench, you should strongly think about taking him, as he easily dominates these selections with win rates over 54% against each ofthem.