Smash the Dragon Achievement?

How does one get this Achievement?

From the description in the Achievement it seems like you need to break his breakbar 5 times in a single encounter, but at most I have seen him get three breakbars with large groups. Hence assuming you are well organised and break his bar all the time, random players who do not care will kill him as quickly as possible and destroy your attempt.

Can you Spawn it with a guild? How big a group is minimum for you to beat it?

The description for Smash the Dragon, “Complete the fight without the Shatterer ever taking off and using Shard Storm.” doesn’t mention a number.
There’s no minimum amount of times per encounter. You just need to break it as many times needed so he doesn’t take off at all.

my bad sorry, must have got confused with seeing my progress with No Fly Zone and some confusing things I picked up from map chat. Thanks for the reply. Still a hard achieve though :/

@"Omnicron.2467" said:my bad sorry, must have got confused with seeing my progress with No Fly Zone and some confusing things I picked up from map chat. Thanks for the reply. Still a hard achieve though :/

The instance needs to include enough people who understand how to break the bar efficiently. That turns out to be smaller than "everyone on the map" but larger than a small party of friends. Usually the best way is to look in LFG for an organized map and during "prime time" is usually the best opportunity to find such groups. Alternatively, you can organize your own, although that is obviously more effort than most people are willing to invest.