Keep it 100

This achievement can be done with Yang or Blake since their combos take a while and they are easy to do, I suggest getting Blake and the stun shot skill from the ranged weapon, you can attack them close range and then run away so you won't get hit, and then shoot them from a distance, you need to learn how to counter attack (by pressing F) at the right time, once they are stunned (after the ranged attacks) you can go for hits, to make it even easier for you, Blake has a perk that extends the time before the combo counter resets, this perk is unlocked at level 10. This achievement can be unlocked on singleplayer and it isn't that hard at all especially if you play on higher difficulties, just hit 100 on the combo hit meter, it can be done on any level, I did it on Chapter 7 at the first grimm area. But since the release of Horde Mode that might be your best and easiest option to do it.