No unlock to date has required using a mechanic that a hero can't do by themselves, or against a required villain, or in a required environment. Since he can't redirect villain damage to himself by himself, I'm confident that won't be required.
Random game of Haka, Naturalist and Bunker vs. The Chairman in Time Cataclysm.
Haka destroyed every non-hero target in the game with Punish the Weak while those targets were the weakest target and put them under Savage Mana. (including the Chairman, because it was fun) Did a whole lot of damage with Rampages, but none to the heroes. At the end, 22 cards under Savage Mana plus a 33 point Haka of Battle boost took out the Operative.
Pydro already commented on the first two but Greatest Legacy is more of an exception rather than the rule. It's also why he is the only variant so far that can't be unlocked in multiplayer since no player is controlling the hero being unlocked.
Still, though, the statement was no unlock to date required a character to do something they couldn't normally.
I really don't think there are hard and fast rules like that. We've seen a number of different combinations required. If I was to speculate, I'd say these unlocks are probably less complex than some in the past because of their relatively rapid-fire nature. Christopher and the game devs probably realize that if it's taking us weeks to figure out each of them, the whole thing's going to get bogged down and frustrating. Better to let them be simpler and let the excitement of the hunt get both rewarded with success and renewed each week.
Cards defnitely played: Ta Moko, Elbow Smash, Dominion (but not all three), Ground Pound, Vitality Surge, Rampage, Punish the Weak.
Cards definitely not played: Any of the Hakas, Taiaha, Mere, Enduring Intercession, Savage Mana.
Haka did all the work killing things (Magmarian, Device, Crystalloid Behemoth, didn't really matter. If it was there, Haka punched it, just in case). Wraith and Legacy did damage but no kills. Some devices and a magmarian died to charged attacks damage (Wraith drew precisely zero Grappling Hooks so that card was extra painful). Taiaha would have made it a lot easier!
No Savage Mana, Enduring Intercession, weapons, or Hakas makes this much easier (and nearly the opposite of what I would have guessed). He didn't kill all the Magmen. How many Behemoths did he kill? (One of my guesses was that he had to kill all three.)
With Rampage, there might have been a requirement to deal a certain amount of damage (possibly without using weapons or Haka of Battle).
This is a non-unlock game, I was just kind of messing around to see how easy this is to get. Haka played all of Ground Pound and Savage Mana, killed a bunch of stuff, only ate one because he got SM late in the game. I was specifically trying to avoid Taiaha and Mere, but that's not enough by itself.
Ambuscade, Magmaria. Using normal Haka, Greatest Legacy, Tempest, Argent Adept, and Captain Cosmic.
Played Savage Mana, and won with it. No hakas, no weapons used. Also did not use Enduring Intercession.
I made sure to defeat every Magmarian at least once using damage from Haka. No other hero defeated any targets. All of them dealt damage, but no ko's with anyone except Haka (and the villain and environment.) Argent Adept destroyed a handful of non-targets, though.
Got it as well. Unfortunately it's very close to pwatson's. I played exactly the cards he described and no others and had no other heroes kill anything. FS Parse, G.Legacy, F6 Tempest, and Haka vs. Gloomweaver in Magmaria. Haka did kill and collect all three behemoths and collected all three smoldering crystals. However, I do have a log (omitting the last power phase in which I won, because Android). The final move was to have Parse use her power, which enabled Tempest to heal everyone to full and Haka to play Rampage to wipe the board.
Just played a game against Ambuscade in Magmaria.
Haka killed every target, and only played Rampage, elbow smash, 1 Dominion, and that’s it. No unlock.
I suspect I needed to deal more damage and/or destroy more targets; I only saw about 6. It was a very short game.
Interesting pwatson, I also had an attempt with Haka doing the majority of the work without unlock. There may have been a few kills here or there, but Haka was trying to kill everything to get it under Savage Mana. He got all the Magamarians, not quite all the Crystalloid Behmoth's and many of Ambuscade's targets (and even a Decoy Projection).
I'm attaching the failed log for comparison purposes (with my game rewinds removed).
Edit: Hmm, I see no kills from other heroes, the only other kill via damage was a Crystalloid Behemoth taking out a Sonic Mine. This is interesting...
Yep, you played both Taiaha and Mere. TakeWalker and McBehrer both didn't destroy many targets, so I'm suspecting it's something like: In Magmaria, win a game in which Haka destroyed at least 10 targets and did not play (or use) either Taiaha or Mere.