Currently this achievement only works with the following Seals:Dredgen (from Gambit), Unbroken (from Crucible), Cursebreaker (from the Dreaming City) and Rivensbane (from the Last Wish raid).
By far the easiest of these is Cursebreaker, but it is tied to many time-gated events and takes many weekly resets to get everything, and also, you need to complete the Dreaming City collection tab, which as of Season of the Chosen is not possible because of a pulse rifle tied to The Corrupted nightfall, which is not on the nightfall rotation this season. Cursebreaker can be completed totally solo though, which might attract more players.
Dredgen is probably the second easiest, but it's tied to the most dreaded mode in the game, which is Gambit. By far the worst triumph from this seal is resetting your infamy rank, but the grind is much easier on double/triple Infamy gain weeks. The other hard part is invading and killing 4 guardians (the whole team or at least a repeated kill of someone who respawned) 3 times. That might take a lot of practice, luck and patience. I used Warlock with Chaos Reach and the Xenophage machine gun, but for some people the new Eyes of Tomorrow exotic might work. I rarely see other supers who are very effecting in killing multiple guardians during an invasion. Maybe Dawnblade or a Hunter with a Arc Staff or a Golden Gun and a great aim. Snipers are great for this as well, if you're good with them, considering the layout of Gambit maps. If you pull that off, you even knock a step of the Malfeasance exotic revolver quest. The last hard part is getting the Triumph Protect the Runner, which requires a single player deposit 75 motes (you need 100 to summon a primeval). I got that by accident in a random game, but if you're struggling, it's good to get a fireteam and get organized. I'm not sure, but it might work if you also lose motes from blockers and keep getting more and depositing, until you reach 75 deposited.
Unbroken is a title I'll probably never get, because of the competitive playlist (and me not enjoying Crucible at all), but if you enjoy the game mode the requirements aren't very hard. Mind that there's a time-gated triumph here as well, requiring you to reach max Valor and Glory ranks in 3 different seasons (that's almost one whole year)
Rivensbane is probably the hardest of all these titles, because on top of completing many different challenges in the Last Wish raid, you also have to complete it flawlessly (no deaths on the whole team), so good luck if you try that.
Previously other titles were present in the game and worked for this achievement, with Wayfarer being the easiest of all (despite a lot of timegated stuff) but with the Beyond Light expansion they were removed from the game.
P.S: When I unlocked Dredgen the achievement didn't immediately pop, if that happens to you just restart the game and log in again. When I did that, the achievement popped.