Quote Originally Posted by Vidu View Post
There is visual confirmation that you have not beaten an NPC (or gotten all cards yet) - kinda the opposite of what you're asking for, but should work aswell?

Any NPC you have not beaten yet will have a triple triad symbol with an exclamation mark above their head and the same symbol will appear on the map.
Any NPC you have beaten, but still have cards to win from will have a triple triad symbol with a star above their head and the same symbol will appear on the map.
Any NPC you have beaten will no longer have any marker above their head or on the map.
While this is indeed useful i think the problem OP has is those TT NPCs who are not visible due to being locked behind a quest. I was doing some unfinished HW quest the other day and by my surprise there was a TT NPC locked behind them. It was a nice surprise for me, but i can see the problem for people who need the achievement/cards.