Aside from the combat challenges, a very good and easy spot to get this achievement is pretty early on in the Story. When you come to the part in which you have to save the doctors in the medical facility, go to Dr. Chen. When you approach him a cutscene will start and goons start to attack you. Just keep a clean slate in this fight and you will get around a 50+combo.
Why this is a good spot to get this achievement is simple: it is pretty early in the game. There won't be any special enemies, everything you have to do is punch, jump, punch, counter, punch .... and so on and so forth.
If you want to do this in a combat challenge, please refer to the video below.
(Video credit: MrBlingBlingNr1)
Hope this helps you guys.
Any improvements? Please let me know in the comments below!