Villain does seem to matter. I tried your technique with Baron Blade and it didn't work. I tried again with Ambuscade and it did. The only other perceivable difference between my tests was that the successful one had an extra hero, using Rook City Wraith (to help accelerate the Environment deck). Number of heroes isn't important, given your input.
In terms of cards in play, the first test had Taiaha, Savage Mana and I think Tā Moko in play. The successful test only had Taiaha and Tā Moko. I don't think those cards are important to the unlock.
So it does seem to be Haka defeats Ambuscade in Final Wasteland with Ancient Library in play and all other heroes incapacitated or removed from play and having played all three Hakas as you suggest.
If it's not that, perhaps you need a certain quota of defeated heroes instead of all others?
What else could it be? If it was a card Haka had in play, it could only be Taiaha or Tā Moko, though. I'm fairly sure I limited my plays in my successful attempt to those and didn't play Savage Mana. In fact, I guess I still have the log of that game, I can go check it out...
I know I never played Rampage, Enduring Intercession nor Punish the Weak, as I was actively avoiding those cards. I did throw in an Elbow Smash or two, and I think I used Ground Pound as well (to keep Ambuscade safe from the Environment while I waited to draw Haka of Battle).
Oh wait, I think I had Dominion in play too now that I think about it more... time to check...
Haka, AZ, and Fanatic vs Ambuscade in Final Wasteland.
All three hakas played, Haka last man standing (barely, used Taiaha to knock out AZ then Ambuscade on last turn). Library, a New Jersey Devil, and Unforgiving Wasteland in play at end (had Con's Bunker out for most of the game until I got the Library in play, though). No Villain cards in play.
Haka cards in play at game's end: Taiaha, Mere, Ta Moko, and Savage Mana. I had also played an Elbow Smash, a Rampage, and a Vitality Surge at some point. Haka ended with 9 HP remaining and 13 cards under Savage Mana, but I don't remember exactly which cards (a combination of Devices and Environment targets).
Had not cleared out any decks with either Savage Mana or with Unforgiving Wasteland (although several cards had been removed that way). Both other heroes incidentally taken out by friendly fire (Haka knocked out Fanatic with a Rampage and AZ with Taiaha).
This didn't wind up testing any specific conditions unknown in prior unlocks (I intentionally even chose a specific team to mimic prior successes), but I tried to remember what had been played by Haka throughout. Hope that helps the general sleuthing.
Edit - after the Rampage, I may have wound up with at least one of each Environment target under Savage Mana - I don't remember if I had a New Jersey Devil under there or not. Pretty sure about all the others.
It's not Savage Mana. Here's all the cards Haka played in my successful run (confiurmed by viewing the log file):
Haka of Shielding
Taiaha
Tā Moko
Haka of Restoration
Dominion
Ground Pound
Haka of Restoration
Haka of Battle
Elbow Smash
So I never even played Savage Mana that time. I did have Tā Moko and Dominion in play, so perhaps one of those, or perhaps Ground Pound.
Then again, it might even be something simple like "play 4 cards with Haka in the title" rather than "play all 3 cards with Haka in the title"...
Did anyone get the unlock while only using exactly three Haka cards?
Edit: For those that want to check their own log files, it has to be either your most recent or second-most recent game, I believe. In Windows, the files for these runs can be found at:
C:\Users\<username>\AppData\LocalLow\Handelabra Games Inc_\Sentinels\log.txt
C:\Users\<username>\AppData\LocalLow\Handelabra Games Inc_\Sentinels\log-copy.txt
The Wraith uses the power on Rook City Wraith. Revealed card: Unforgiving Wasteland Rook City Wraith moved Unforgiving Wasteland from The Final Wasteland's revealed cards to the environment trash.
From a thematic point of view, it would make sense for Haka to be the last man standing with access to the Library. Beyond that, an additional thought I had is if you have to discard Haka cards during the game, which is part of the innate power of Eternal Haka.
I played exactly 3 "Haka of X" cards (one of each type). I did discard a single Haka of Shielding to boost my play of Haka of Battle.
I never had to destroy any of Haka's Ongoing/Equipment cards I got in play. Cards we had in common between our two games (checked my logs - thanks for the heads-up on that):
Haka of Shielding
Taiaha
Tā Moko
Haka of Restoration
Haka of Battle
Elbow Smash
Maybe Haka last man against Ambuscade in FW, all three hakas played, Tā Moko in play (thematically to represent his resilience?), Library in play?
Got the unlock this morning. Haka, Fixer, D. Visionary vs Ambuscade in Final Wasteland. Library, Unforgiving Wasteland and Abominable Snowman in play. I think the only thing UW took out of the game was a decoy projection. Whittled Ambuscade down then Fixer incapped Visionary and himself. Haka had Taiaha, Mere, Dominion, TaMoko and Savage Mana w/2 cards under it in play. Had used 1 each of the hakas before hand. Final Round, used a Haka of Battle for a 20 point Savage Mana. I think he only made use of the library once since it came out.
Might be a long shot, but was Con's bunker played at any point in the game for any of your unlocks? I kept that, the Library and Unforgiving Wasteland in play the whole time.
Unlocked against Ambuscade in Final Wasteland. Used a big savage mana burst to take him down after Legacy had been incapped and Tachyon had been removed from game by the environment. Had in play Te Moko, Mere, Savage Mana, Dominion, Taiaha, and Punish the Weak. Had Snowman, Unforgiving WasteIand, Ancient Library, and Con's Bunker all out. Made it a point to have Haka draw from Ancient Library several times, including on the winning turn, just in case that was an aspect of the assumed Ancient Library requirement. Made sure to take out the last non-environment target (a tank) before taking out Ambuscade, also. I did use each Haka once, and Restoration twice, discard all manner of cards---thanks to SST Tachyon, I did cycle through Haka's deck, which also struck me as the kind of small requirement that fits Handelabra's pattern, would match the flavor of Eternal Haka, but be easy to overlook having fulfilled (or not).