Interesting question that has been raised in the Steam forum:

http://steamcommunity.com/app/291650/discussions/0/1319962599255308386/

 

Since it's possible to finish the "Regrets Worth Trading quest - http://pillarsofeternity.gamepedia.com/Regrets_Worth_Trading - in several ways including peaceful resolution or killing Lafda, that can lead to Asca not offering the Lafda Bounty in TWM 2:

http://pillarsofeternity.gamepedia.com/Bounty:_Lafda

 

Is it known whether that bounty is a requirement for getting The Ultimate achievement?

 

Edited May 13, 20178 yr by Belfaldurnik

An the answer to the question is:

 

No.

 

The game handles the Lafda bounty as optional, so it is not needed for unlocking The Ultimate achievement.