I had a much harder time ranking the villains than I did the heroes, since a lot of them don't have as much storyline descriptions of their powers. A couple of them don't really even seem to be measurable on a strength scale because they aren't physical entities (Gloomweaver, Wager Master). I'm assuming that all the Ennead members have superhuman strength simply because they're gods, though the card mechanics don't really imply that.
Here's what I got:
The giants:
Akash'Bhuta: she's the size of a mountain
Omnitron: it's a mobile factory
Progeny: it's a 10 to 30 foot tall metal monster
Iron Legacy: he's off-the-charts strong
The superhumanly strong:
The more physical members of the Ennead (Geb, Tefnut, Nuit)
Apostate: he's as strong as Fanatic, and she can hurl tanks from the sky
The average members of the Ennead (Atum, Osiris, Set)
Gloomweaver's skinwalker form
The more mystic and less physical members of the Ennead (Nephthys, Isis, Shu)
Augmented Strength:
Plague Rat
Bugbear
Kaargra Warfang: she's an alien warrior and queen of an arena. It's unclear how much of her melee damage comes from strength vs skill, though.
Grand Warlord Voss: as much as he looks like Darkseid, his background makes him sound a lot less overpowered. He's a badass, but not an out of control one.
Fright Train: I'm not sure how strong he is. He looks and sounds like Juggernaut, but his background says his strength comes from cybernetics and drugs. I figure at the least, he's stronger than Spite.
Spite
Deadline: he's an 8' tall alien, and he swings a pole arm around. He looks pretty strong.
Ambuscade: none of his cards have him using his strength as a power, but he's got a robot arm, and there's a card art showing him dangling a hostage off a roof one-handed.
Greazer Clutch: it's a comic trope that aliens are stronger than humans, but there's not much in Greazer's deck to indicate that he's super strong. He seems to rely on speed and cleverness, mostly.
Biomancer: I have no idea how strong he is, but he keeps himself alive with foul magics, so his body is probably at least a little augmented.
Pretty strong, but on a human scale
Chairman: is a "perfect human specimen"
Operative: is also a "perfect human specimen"
Citizen Anvil: strong enough to fight with hammer and shield
Proletariat: also strong enough to fight with sledgehammers
Sergeant Steel: professional soldier, though he relies on ranged weapons
Kismet: she's shown punching out Setback. Is she as strong as he is? Or just psycho and violent?
Baron Blade: for a mad scientist, he seems pretty willing to mix it up in melee. Maybe he should be listed higher, if he's using augmentation drugs or wearing his SABER suit.
La Capitan
Ermine
Normal human strength:
Citizen Dawn: I wonder if being able to fly provides a little bit of extra strength, simply in terms of leverage? I'm not sure.
Friction
Infinitor
Citizen Hammer
Chokepoint
Miss Information
Matriarch
Low human strength:
Dreamer: not only is she a kid, but isn't she also in a coma?
I would bump Dawn up a level. She absorbs light energy and uses it to augement herself. She generally uses it in the form of energy blasts, but I'm sure she could be very physically destructive if she wanted to be, more than Biomancer who it would seem probably just has a metal skeleton.
Also, Kaagra should defintely be up a few levels. Sky-Scraper felt the need to go huge to take her on, and I'm sure that as a nemesis match-up, it was probably decently even.
Plague Rat rips apart the Bunker suit in one of his cards, and seems to have beaten Fanatic in another, he's defintely a physical threat, throwing KNYFE through a wall in his Villains version.
Bugbear has cracked roads, ether from jumping or stomping it is hard to say, but we also see Naturalist running, so clearly the guy who can turn into a Rhino thinks Bugbear is too strong to tackle head on. I wouldn't be surprised if Bugbear could lift a truck with ease.
While the memebers of the Ennead who don't focus on the Physical, like Shu who is made of Air are probably signifigantly weaker in the physical sense, barely topping over human and relying on their magick to fight for them.
1) I would be cautious about equating size and strength. It seems like a no brainer, but I think there is a trap when it comes to comic book logic (if such a thing exists)
2) With number 1 in mind, lets look at Grand Warlord Voss. I think you are vastly underrating this dude. This guy is shown to go toe-to-toe with Legacy. It is not a stretch, therefore, to think that he is much closer to Iron Legacy in these catagories. In the game Voss might be a push over at times, but in my mind from a comic perspective, Voss is one of the largest threats the heroes ever faced. Need some contextual proof? Our heroes couldn't fully defeat Voss! Never did. They had to resort to banishing him to another dimension to get rid of him. You can't say the same of Omnitron, Akash, or even Progeny (who I think is the single strongest on this list).
3) Putting Ambuscade on the same loose level of strength as Fright Train feels way out of place. I understand the catagory though and find it hard to argue that he is not augmented so I'm ok with it. But with the same token, you can make a strong case that Chairman/Operative/Citizens/Kismet/Pro/Baron/Chokepoint all have "augmented strength. Ambuscade was augmented by science, but wasn't Chairman and Operative augmented by science just in a different way (oh, and mystical forces as well). Citizens are (largely with some exception) born with powers. Anvils powers surely augment him above a human lvl teir. Baron and Pro both are augmented by science like Ambuscade. The "pretty strong" and "augmented" teirs I think need tweaks and some looking at.
4) Ermine above Dawn? Heck, Ermine above anyone? Ermine is a common theif who couldn't punch her way out of a paper bag. She could sneak out of it, but she ain't hitting it.
I like these lists though! Its fun to think about.
They are. I wonder if the problem is trying to do 6 tiers. Breaking it into 10 tiers, we can get:
Tier 10 (strength difficult to measure)
Grand Warlord Voss (if he's the Darkseid/Thanos archetype, then he's probably the single strongest character in the setting)
Iron Legacy
Progeny
Akash'Bhuta (as strong as a mountain)
Legacy
Geb (he looks like the biggest and strongest of the Ennead)
Tier 9 (strong as a train)
Omnitron (as a flying factory, probably fits "strong as a train" tier)
Haka (he might belong in Tier 10. I'm not sure)
Fright Train (if he's the Juggernaut archetype, then he's going to be remarkably strong)
Mainstay (if he's the Ben Grimm archetype, then he's going to be really strong)
Anubis (he's one of the bigger Egyptian gods, though none of his cards seem to imply super strength)
Atum (he's the second largest Ennead member, in their group portait, though his card doesn't really indicate super strength)
Tier 8 (strong as a tank)
Young Legacy (she can list a bus one-handed. Might be tier 9)
Apostate (seems to be bigger and stronger than Fanatic, but by how much?)
Fanatic (Final Dive implies she can drop fairly heavy things from on high. Also, she's flying with 100 lbs of gear)
Bunker (literally a walking tank)
K.N.Y.F.E. (her super suit makes her really strong, but I'm not clear how strong)
Benchmark (maybe?)
Tefnut (the other main source of melee damage in the Ennead other than Geb, and she seems like their main warrior)
Ra (none of his powers indicate super strength, but he is a god. Maybe he should be lower)
Nephthys (creepy fire breathing woman, seems pretty supernatural. Maybe she should be lower.)
Tier 7 (strong as a car)
Kaargra Warfang (maybe she should be higher, especially if she fills the Mongul archetype)
Plague Rat (can go through walls, and with enough time, crack open Bunker)
Bugbear (also seems super strong)
Setback (his bio mentions boosted strength, but I'm not sure how much he's boosted)
Zhu Long (his dragon form might require a higher strength tier; it's unclear how big and strong he really is)
Gloomweaver (his skinwalker form looks pretty strong)
Absolute Zero (his suit probably gives him mild augmented strength)
Isis (flying godling - I'm assuming she's comperable to Fanatic, but a little less strong)
Nuit (seems like a decent tier for "average Ennead")
Osiris (seems like a decent tier for "average Ennead")
Set (seems like a decent tier for "average Ennead")
Tier 6 (strong as a bear)
Blood Countess Bathory (she's a vampire. Vampires are strong)
Spite (the drugs should make him pretty augmented, but not wildly super strong)
Abuscade (augmented, but by how much?)
Deadline (none of his cards indicate super strength, but he's like 8' tall)
Guise (I don't really know where to put this guy)
Omnitron-X (he's a robot, and probably a little stronger than a human, but maybe not by much)
Sky-Scraper (none of her cards indicate super strength, but she's the same species as Voss, so it seems reasonable for her to be strong)
Tempest (none of his cards indicate super strength, but he can swim at depth, which implies some strength)
Shu (as a wispy smoky thing, probably weaker than the other Ennead)
Tier 5 (strong as a horse)
Chairman (augmented to the absolute peak of human ability)
Operative (augmented to the absolute peak of human ability; not sure if she's as strong as Chairman though, maybe should be down a level)
Citizen Anvil (seems like he's got some super strength going on, but not sure how much)
Tier 4 (exceptional human strength)
Mr. Fixer (he seems pretty strong)
Biomancer (none of his cards indicate super strength, but he seems capable of augmenting his body)
Baron Blade (he seems pretty athletic even at a baseline. His combat drugs probably push him up to Spite's level, and his super suit probably pushes him to Bunker's)
Greazer Clutch (he seems pretty strong)
Proletariat (he fights with a giant hammer)
Sergeant Steel (he looks really brawny)
Tier 3 (above average human strength)
Wraith (martial artist)
La Capitan (sword fighter)
Parse (archer)
Expatriette (carries lots of firepower around)
Citizen Dawn (does she have augmented strength? I'm not sure)
Kismet (does she have augmented strength like Setback? It doesn't seem like it. She's pretty punchy though.)
Chrono-Ranger (his base strength is probably here, and his robot arm is probably a bit stronger)
Infinitor (he was a cop, and probably decently strong)
Writhe (no idea where his strength should be)
Ermine (she's some kind of acrobat, so probably pretty strong)
Tier 2 (average human strength)
Naturalist (in his human form; he looks athletic, so maybe he should be tier 3)
Scholar (base form; not sure how strong his elemental forms are, though)
Captain Cosmic
Agent Adept
Chokepoint
Citizen Hammer
Dr. Medico (he's nearly weightless, but the sentinels deck will let him do melee damage all the same)
Friction
Matriarch
Miss Information
Nightmist
Tachyon
Unity
Visionary
Tier 1 (Below average strength)
Wager Master (note: this is where I'd put his "native" strength when he's not augmenting it with his reality control powers)