How to counter Graves
Let us take a look on how to beat Graves. We will look at champions who are strong against Graves and who are weak against Graves. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Jungle champion who counters Graves. You can already win in champion select with the right counters for Graves. If you want to know how to counter Graves then you need to take into account the best picks vs Graves and the worst picks vs Graves. This Graves counter data is based on matches played by Pros on patch 15.14 and previous ones. It is important to see whether Pros counter picked Graves or whether they played as Graves.
Champions used by Pros to counter pick Graves
Looking at the matches from Pros (see table Pros counter picked Graves) we can see that they picked 
Lee Sin most often to counter pick Graves. The matchup Lee Sin vs Graves occured 12 times. Graves has 8 wins and 4 losses in this matchup. Learn how to counter pick Lee Sin to get another perspective on the data.
Lane outcome for Graves
When looking at Graves 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 Graves. The lane outcome of Graves consists of three outcomes: Win, Loss or Draw. Let's take a look of Graves 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 Graves.
Conclusion
Analyze the available data and learn how to beat Graves. To master Graves take also a look on Graves builds and runes for Graves. Good luck, Summoner!