Whats the name for the achievement 10x Triple Frag in the campaign..
and
where Could I do it easily?

I forget the name, but an easy place is if you remember in the first level when the locust are opening that door with liek a saw or somehting, throw a frag under the door right before they open it.
rinse adn repeat!

its called clusterluck...and its not just frags, its just a triple kill, in either campaign or online

and Snoboy's place to do it is definately the easiest