"That Had to Burn" Boss Achievment
According to the wiki:
Bug: The achievement no longer triggers regardless of how many times the Megalaser fires, since the September 17, 2013 update in which the Tequatl fight was overhauled.
It is currently unobtainable, although ANet has been silent on whether this is something they intend on fixing (either by making it achievable again, or by moving the achievement to the historical category).
Personally I think they should make it achievable again, and automatically grant it to anybody who has the “Burning Light” achievement. Even though we’re not firing the Megalaser at Tequatl personally, from a logical perspective, isn’t that the same as what the achievement is asking? That Had to Burn can become the reward from the first time the player succeeds at a defense event; Burning Light is for succeeding at three consecutive defense events in the same battle.
I got this achievement today while killing stuff around the north cannons during the first battery event. The achievement awarded when the canon fired. This may have been a fluke or a way to get the achieve to work; I suggest others test it further.
It was fixed and the wiki article was updated 2 June, around the time this thread was created.