Knack 2 - Combo King Trophy Guide - Equipped a combo meter and landed a 100-hit combo. [Bronze]

Chapter 5-4 (Normal Difficulty recommended)
First of all, you must unlock the combo meter gadget. It consists of 5 parts found in treasure chests (it's random what reward a chest gives you).

Enable the gadget and a combo counter will show up in the top left corner. You must do 100 hits in a row without being hit!
The best place to farm hits is the end of chapter 5-4. There are many waves of enemies spawning. You can replay this chapter at any time via chapter select (world map).
Kill all the enemies by holding Square-Button (requires Multi Strike skill). The Multi Strike does lots of hits all at once. Try to kill the enemies one by one. You can also throw boomerangs to stun them (hold Triangle , you learn this move automatically from Ava).

At this point of the story it's very unlikely that you have unlocked the combo meter. Therefore, it's highly recommended you come back after the story. You can get around 150 hits from this one enemy encounter.

If you get hit, transform to small knack and let the enemies kill you. This will restart the checkpoint and you can try again.
It's recommended to do this on normal difficulty. On easy the enemies die too quickly and on hard they are much more aggressive and might hit you.