Kung Fu Panda 2

After you completed the story mode, you'll probably notice that some achievements like this one, are not unlocked. This will unlock while doing some progress on the other achievements.

you will have to do combat challenges while going for all medals in the Free Play mode. These are plain challenges that you've come across during the game or with just a little variation. (instead of throwing at monkeys trying to kill you, they've put in one with bunnies throwing snowballs)

Though some might unlock it while playing story mode, by getting it by killing for example 3/4 gorillas and then die and restart. I haven't tested that one and i'll probably unlock all the others that i haven't while playing the challenge mode.

I found that after completing the story and working on gold medals for each challenge at each difficulty this amount came naturally before I finished them, so I wouldn't worry too much about grinding it out

If you do want to grind this out then the combat challenge in the Shantou Palace has gorillas, hard difficulty has the most