The First triumph that is near impossible to get is the beyond light Heroic Guardian one, which details in a fireteam complete heroic patrols on europa. For me its been 4 days of searching for them they don't spawn at all anymore. Second triumph is the flawless Zero hour mission triumph I have the solo flawless of it but not the "flawless" of it. And I did it also with a fireteam which everyone else died but me but completed it flawless.