Fairytale Fights

This achievement is easiest done on Chapter 1: On the trail.

Once you have picked up the carrot after the bridge, proceed forward an you will be attacked by lumberjacks. Just keep wailing on them until your combo count goes over 50 hits. Your combo count will reset if you are hit or if you take too long between each of your strikes.

***raidenhardcore adds***
halfway on the fifth level (toy/candy factory) right before pied piper boss, there is a clearly visible chest when hit pops 6-7 toy rabbit blunt weapon, right after that you get 6-7 enemies which you can hit with that toy rabbit, you get easy over 100 combo hits (i got 112 and was even hit once), just make sure you are not hit in between.
just to add your hit counter is in the bottom left corner so you can keep an eye on that it pops when your counter resets

Your mileage may vary, but I got this in the "Little Kingdoms" chapter on the level where the fairy godmothers appear. At one point a godmother shows up by herself in a bedroom (the room is just to the right of a wishing well). With a one-star blunt weapon (a toy rabbit in my case) it's easy to run up to the godmother and hit her repeatedly with the soft weapon at close range and run up the combo meter; I got the meter up to 64 hits.

The key is to use a one-star weapon: this level has a few pillows that will do the job, and you may be able to get a toy rabbit from the wishing well if you're lucky.

If you're like me and keep getting hit trying to get a 50 hit combo, then I think this method is for you:

You need three controllers however. One to be signed in as you and 2 guests signed in. Then press start (In Taleville) and go to Level Select, then Arena and choose Appendix 1. No time limit and 10 points to win. (More if you think you might mess up)

Now press start on the controllers to get them in the game. Now start at the bottom (You start here anyway) and have one guest on one side of you and the other guest on the other side. (DO NOT GRAB A WEAPON) Now start smacking one the guests with the right stick (I think it takes 9 hits to kill them or so). When the guest dies, quickly run to the other guest and beat them up before your combo is broken. Simultaneously press A on the dead guest's controller to revive him so that when you kill the other guest, you can run back to them. Continue this until you have a 50 hit combo. The achievement pops after the combo has timed out.