You remember Durnehviir the dragon from the beyond death quest? In your conversation with him on your way to leave the Soul Cairn he gives you a shout to be able to summon him in Tamriel. Buy all three words of the shout.
Now each time you summon him in Tamriel he will teach you a word for a shout called soul tear. Summon him 3 times and the achievements yours. The shout must be aimed at the ground while charging the shout otherwise it will not summon him.
The main issue unlocking this achievement is finding a spot to summon him in. Since he needs to be able to fit uninterrupted. The windmills by whiterun worked for me and others aswell the area across the water from Harkon's castle. Also make sure to charge up the shout otherwise it won't summon him.