How to counter Tryndamere
Let us take a look on how to beat Tryndamere. We will look at champions who are strong against Tryndamere and who are weak against Tryndamere. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Mid champion who counters Tryndamere. You can already win in champion select with the right counters for Tryndamere. If you want to know how to counter Tryndamere then you need to take into account the best picks vs Tryndamere and the worst picks vs Tryndamere. This Tryndamere counter data is based on matches played by Pros on patch 14.9 and previous ones. It is important to see whether Pros counter picked Tryndamere or whether they played as Tryndamere.
Champions used by Pros to counter pick Tryndamere
Looking at the matches from Pros (see table Pros counter picked Tryndamere) we can see that they picked 
Akali most often to counter pick Tryndamere. The matchup Akali vs Tryndamere occured 2 times. Tryndamere has 2 wins and 0 losses in this matchup. Learn how to counter pick Akali to get another perspective on the data.
Lane outcome for Tryndamere
When looking at Tryndamere 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 Tryndamere. The lane outcome of Tryndamere consists of three outcomes: Win, Loss or Draw. Let's take a look of Tryndamere 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 Tryndamere.
Conclusion
Analyze the available data and learn how to beat Tryndamere. To master Tryndamere take also a look on Tryndamere builds and runes for Tryndamere. Good luck, Summoner!