How to counter Vel'Koz
Let us take a look on how to beat Vel'Koz. We will look at champions who are strong against Vel'Koz and who are weak against Vel'Koz. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Mid champion who counters Vel'Koz. You can already win in champion select with the right counters for Vel'Koz. If you want to know how to counter Vel'Koz then you need to take into account the best picks vs Vel'Koz and the worst picks vs Vel'Koz. This Vel'Koz counter data is based on matches played by Pros on patch 13.24 and previous ones. It is important to see whether Pros counter picked Vel'Koz or whether they played as Vel'Koz.
Champions used by Pros to counter pick Vel'Koz
Looking at the matches from Pros (see table Pros counter picked Vel'Koz) we can see that they picked 
Orianna most often to counter pick Vel'Koz. The matchup Orianna vs Vel'Koz occured 2 times. Vel'Koz has 2 wins and 0 losses in this matchup. Learn how to counter pick Orianna to get another perspective on the data.
Lane outcome for Vel'Koz
When looking at Vel'Koz counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Vel'Koz. The lane outcome of Vel'Koz consists of three outcomes: Win, Loss or Draw. Let's take a look of Vel'Koz lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Vel'Koz.
Conclusion
Analyze the available data and learn how to beat Vel'Koz. To master Vel'Koz take also a look on Vel'Koz builds and runes for Vel'Koz. Good luck, Summoner!