As of today, we have a list of trophies/achievements in Destiny. It is not specific if this is all them or if any have been omitted due to being story related (AKA spoilers). You can check out the list here at the bottom of this post over at Bungie: http://www.bungie.net/7_Bungie-Weekly-Update---06272014/en/News/News?aid=11607
Of course the one achievement/trophy worth looking at is the one that mentions killing a champion of the Dark. The name is dragon slayer, so I wonder if that is by chance a clue as to what the fifth enemy in Destiny will look like. Although I'm not sure if I'd be happy or disappointed if the Darkness ended up being a fleet of space dragons.
Another thing worth noting is the fact that there is mention of a hard difficulty for raids. Raids are already supposed to be the hardest PvE content available in the game, so it is hard to imagine anything harder than that. Heck even during the Alpha, the Strike known as Devil's Lair was really difficult when it was done at level 6 (not so much at level 8 when everyone had BiS alpha gear), so I can't possibly imagine what something even harder would be like.
Some of the more annoying trophies/achievements will be the PVP ones, but those are mostly time consuming. The real challenge will likely be the one where you try to complete a strike without anyone in your fireteam dying.
That is all for now folks, see ya!