How to counter Lux
Let us take a look on how to beat Lux. We will look at champions who are strong against Lux and who are weak against Lux. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Support champion who counters Lux. You can already win in champion select with the right counters for Lux. If you want to know how to counter Lux then you need to take into account the best picks vs Lux and the worst picks vs Lux. This Lux 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 Lux or whether they played as Lux.
Champions used by Pros to counter pick Lux
Looking at the matches from Pros (see table Pros counter picked Lux) we can see that they picked 
Rakan most often to counter pick Lux. The matchup Rakan vs Lux occured 15 times. Lux has 7 wins and 8 losses in this matchup. Learn how to counter pick Rakan to get another perspective on the data.
Lane outcome for Lux
When looking at Lux 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 Lux. The lane outcome of Lux consists of three outcomes: Win, Loss or Draw. Let's take a look of Lux 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 Lux.
Conclusion
Analyze the available data and learn how to beat Lux. To master Lux take also a look on Lux builds and runes for Lux. Good luck, Summoner!