How to counter Twitch
Let us take a look on how to beat Twitch. We will look at champions who are strong against Twitch and who are weak against Twitch. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Adc champion who counters Twitch. You can already win in champion select with the right counters for Twitch. If you want to know how to counter Twitch then you need to take into account the best picks vs Twitch and the worst picks vs Twitch. This Twitch counter data is based on matches played by Pros on patch 14.23 and previous ones. It is important to see whether Pros counter picked Twitch or whether they played as Twitch.
Champions used by Pros to counter pick Twitch
Looking at the matches from Pros (see table Pros counter picked Twitch) we can see that they picked 
Kog'Maw most often to counter pick Twitch. The matchup Kog'Maw vs Twitch occured 15 times. Twitch has 10 wins and 5 losses in this matchup. Learn how to counter pick Kog'Maw to get another perspective on the data.
Lane outcome for Twitch
When looking at Twitch 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 Twitch. The lane outcome of Twitch consists of three outcomes: Win, Loss or Draw. Let's take a look of Twitch 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 Twitch.
Conclusion
Analyze the available data and learn how to beat Twitch. To master Twitch take also a look on Twitch builds and runes for Twitch. Good luck, Summoner!