Here is the full list of all 21 Words of Yendor achievements.
Solved a 3-letter Word of Yendor for the first time
Solved a 5-letter Word of Yendor for the first time
Died at a Showdown
Solved a 4-letter Word of Yendor for the first time
Solved a 6-letter Word of Yendor for the first time
Solved a 7-letter Word of Yendor for the first time
Solved an 8-letter Word of Yendor for the first time
Solved a 9-letter Word of Yendor for the first time
Solved a 10-letter Word of Yendor for the first time
Solved an 11-letter Word of Yendor for the first time
Solved a 12-letter Word of Yendor for the first time
Died at a Graveyard
Died at Traveling Vagabonds
Died at a Rescue
Died at a Tomb
Died at a Factory or a Laboratory
Cured by Dr Creo
Met with Emilie
Met with the Iron Hussars
Visited the Lighthouse
Always chosen the first encounter at every location