I've done the Tachyon ones...and I think I may have done the damage one of Haka's too, with Savage Mana versus the Matriarch (she had something like three or four birdies left in her entire deck, including deck, trash, and cards in play, by then :D). I've let off an Omni-Cannon which was fuelled by Bunker's entire deck apart from two Maintenance Units, which were only left out because I needed two spare cards for Spite to make me put back into my hand via his drug during his turn. I've also Inventory-Barraged stuff at least twice in the past.
Why limit Tachyon to only 63 damage in a turn? You can do much more if you include Sonic Vortex into the mix as well as the 3 Light speeds (or instead of 1), you're making them pretty impossible anyway, why not make them even more impressive?
Or Omnitron after the big guy is dead (you still have to kill all the drones). If you had [redacted] on a target, you could use that to kill a boss maybe when the original target died too.
With Raptor Bots, there are a total of 11 Mechanical Golems in the deck, one if which if in play will always increase damage dealt by Golems by 1 (so, no way out of that buff), which means a total of 13 melee damage from each raptor.
There really is no true limit for Savage Mana, because any target (whether Villain, Environment, or Hero) can be put under Savage Mana. Not only that, but ongoing cards (and I think equipment cards) can become a target as well. If you want a true theoretical max (which, in practice, will never happen), you would have 39 Haka cards, 40 hero cards * 4, 25 villain cards, 15 environment cards, and 1 villain character card (assuming the villain character card can be destroyed, and that it does not win the game). That is 240 cards. At two times, that is 480 damage. But, that is not possible, as there will likely never be every card is a target, and it would be nearly impossible to count the most possible targets in a game.
For Omnicannon, it's 39 cards, at 2x (I believe) for 78.
Technically, the only way that is possible is if all other heroes have been incapacitated prior to using Rampage, as you deal all non hero targets prior to dealing hero targets. I can't think of any villain that has you win after incapacitating a hero, and Haka has no redirection ability (and, any other hero that would be able to give him this redirection ability would have to be incapacitated before redirecting, thus losing the redirection ability, otherwise, when that damage is redirected, it would win the game before all other allies are incapacitated). The only other way is if some villain or some environment gave Haka a redirection ability to redirect his own damage (after defeating all other heroes) to make the finishing strike.
Now, he could use a power after the rampage to make the finishing blow, thus having all heroes incapacitated, but then that is not exactly using Rampage to defeat the villain.
The Realm of Discord has frightening applications indeed for the upper limit of Haka's Savage Potential.
So, theoretically, Realm of Discord against Voss could theoretically claim every card in Voss's deck, +6 (I think?) for the targets in the Realm of Discord. He would have to be Ether-Twisted, so he could claim the spaceships without using Savage Mana. So that's 31, doubled for 62, plus whatever hero ongoings, equipment, and bots you manage to devour.
Which card in the Realm of Discord would be so helpful to Haka? The one where everything comes to life with 6hp? That would also be a threat to Haka's Savage Mana card, then - if there were enough hit-every-target minions out (or whatever) to deal the six damage needed to destroy it, it'd be bye bye Savage Mana ;). But yeah…that'd be pretty cool. Surely, though, that'd work against any villain who used a lot of targets and ongoings? The Matriarch springs to mind…though I suppose Darken the Sky and Raucous thingy are One-Shots…
If you're looking for stupid numbers of damage then kill off Absolute Zero and Fanatic and have Visionary/Nightmist sit in their Cocoon/Mist-form, you can one shot a full HP Akash'bhuta if the cards fall your way.
Hehe yeah...Legacy has a lot of Ongoings as well. And Tempest. And the Adept. It'd be an interesting thing to try, I think - get that animatino card from the Realm of Discord to come up, get Haka to go around beating up everyone's stuff to put it under Savage Mana, then unleash about three or four decks' worth of shit onto whichever unfortunate villain you happen to be playing at the time :D. Though best be careful if it's someone like Akash'Bhuta who can destroy environment cards, or that could spoil your fun ;).
In one of the more recent games I played against Voss, exactly that scenario happened. Voss got both of his capital ships out against a melee-heavy team, and Imbued Vitality came up. Absolution, Savage Mana and Inspiring Presence were just some of the cards that went in the bin. And of course, because Absolution had hit the bin, it was very hard to actually kill the ships.
Yeah, Imbued Vitality threatens Savage Mana, but we're looking at ridiculous scenarios here. I didn't say it'd be easy, but you could certainly inflate Savage Mana in a big way by consuming Hero ongoings and equipment.