Acquire BOTH Hero AND Villain tags early during the stage of Fort Joy.

[Aurelucere]

I don't know if my methods works for you guys, but I tested 3 times in this way and successfully gained both tags on each session. There are 3 things for each tag needed to be done.

For Hero tag:
1) Help other characters escaping the Kraken after the conversation with the 2 kids.
2) Side with Elodie in the shakedown.
3) Reunite Yarrow and Migo.

For Villain tag:
1) Trick Unnis the elf to get her gold through your main character.
2) Sell Stingtail to Griff and save him later.
3) Go through the passage indicated by Amyro and kill the fire slugs after finishing the deceptive dialogues.*

Note:
1) You need to finish these 6 things ASAP because I still not sure if any other incidents might keep you from winning the tags. So playing as an elf with Petpal is the quickest way.
2) It seems only "TRAITOR" actions are counted in the progress toward Villain. Any murder or theft has no effect or does not directly contribute to the tag.
3) Meanwhile, you have to initiate your fight for betrayal by NORMAL attacks. And it is confirmed that, if landing the 1st blow on the fire slugs by any AOE or NON-TARGETED spells, your action CANNOT trigger Villain tag later on.*

Hope it is helpful to others.