How to counter Tahm Kench
Let us take a look on how to beat Tahm Kench. We will look at champions who are strong against Tahm Kench and who are weak against Tahm Kench. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Support champion who counters Tahm Kench. You can already win in champion select with the right counters for Tahm Kench. If you want to know how to counter Tahm Kench then you need to take into account the best picks vs Tahm Kench and the worst picks vs Tahm Kench. This Tahm Kench counter data is based on matches played by Pros on patch 14.12 and previous ones. It is important to see whether Pros counter picked Tahm Kench or whether they played as Tahm Kench.
Champions used by Pros to counter pick Tahm Kench
Looking at the matches from Pros (see table Pros counter picked Tahm Kench) we can see that they picked 
Rell most often to counter pick Tahm Kench. The matchup Rell vs Tahm Kench occured 9 times. Tahm Kench has 5 wins and 4 losses in this matchup. Learn how to counter pick Rell to get another perspective on the data.
Lane outcome for Tahm Kench
When looking at Tahm Kench 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 Tahm Kench. The lane outcome of Tahm Kench consists of three outcomes: Win, Loss or Draw. Let's take a look of Tahm Kench 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 Tahm Kench.
Conclusion
Analyze the available data and learn how to beat Tahm Kench. To master Tahm Kench take also a look on Tahm Kench builds and runes for Tahm Kench. Good luck, Summoner!