So, I was wondering which heroes were actually strongest, and decided to base it off of the melee damage done.
As a baseline, it looks like:
1 melee damage: The Rat Beast and Horrid Skunk Ape do a single melee damage
2 melee damage: The Abominable Snowman, or a single pack of velociraptors
3 melee damage: Collapsing Hallway does this, so this one would be the damage of a building collapsing on you
4 melee damage: ???
5 melee damage: Getting hit by a monorail. Or smacked by the Kraken.
The main doers of melee damage are Mister Fixer, Fanatic, Legacy, and Haka, with an honorable mention to Wraith.
Mr. Fixer does 1 damage, but styles and weapons can push that up. Still, I'm inclined to say Mister Fixer has peak human strength.
Wraith has a combat stance that does 2 melee damage, but that seems to be all skill rather than muscle power.
Chrono-Ranger can do 2 melee with the Terrible Tech Strike, which is robotic, so it seems like robotic limbs are just barely superhuman (note: Omnitron-X's rocket punch is also 2 damage, but it's projectile).
Then we get to the three power houses: Haka, Legacy, and Fanatic.
Haka and Fanatic both do 3 melee with their signature weapons (Absolution and Taiaha). Both seem to do about 2 damage with their unarmed strikes (Smite the Transgressor vs. Crush). However, Haka has the Rampage card, that does 5 base damage (holy crap!). Legacy can thokk for 3, or backfist for 4, doing as much damage unarmed as Haka and Fanatic do armed (though less than rampage). Legacy has Surge of Strength for a sustained damage boost, while Haka has Haka of Battle for massive pushes of damage.
So, I'm inclined to say that Legacy is the strongest, with Fanatic trailing behind. When Haka is calm, he's as strong as Fanatic. However, when he decides to flip out, he can match or exceed Legacy's strength.