The Squadron Supreme has a long history and a reputation as Marvel's direct copy of the Justice League. As the team's roster and history expanded, that direct analogy persisted with new members that reflected later additions to the Justice League.
Here is a comparison of the strongest and weakest members of the Squadron. Strongest shall be defined in this list as most physically powerful. There may be some defined as weaklings that are quite powerful. In most cases, different versions of the characters, specifically J. Michael Straczynski's version, share similar power levels, at least among the versions listed here. One of those is so different, she counts as a different character altogether.
10 Weakest: Arcanna
As a sorceress, Arcanna wields some amazing power. Unfortunately, not much of it is physical. It's almost certain that she has had some combat training, but she doesn't seem to be too focused on building physical strength. If not for one instance of her taking down another member on this list, she might rank even lower on the strength scale.
While in labor, and assuming that she had several months of lessened activity and training, she was fighting the illusion of increased gravity caused by Moonstone. She created her own illusionary double and crawled away to sneak behind Moonstone. With one well-placed sucker punch, she knocked out her opponent.
9 Strongest: Amphibian
Amphibian barely edges out the Skrullian Skymaster for this list. The strength that comes from his undersea adaptation is enough to help him overturn a tank, with the help of Power Princess. Of all of the Squadron, he may have received some of the lightest development before getting featured in Squadron Supreme: New World Order.
It was in that book that it was revealed that the longer he stays in the deep ocean, the more inhuman his appearance becomes to adapt to the environment. This inhuman appearance was incorporated into the version of the character from J. Michael Straczynski's Squadron Supreme series.
8 Weakest: Shape
Shape was a bizarre addition to the Squadron Supreme, being a pastiche of Plastic Man or Elongated Man. Mentally handicapped, he found a home after undergoing the Squadron's behavior modification. Even after having it reversed, Shape remained loyal to the Squadron.
Shape even journeyed with the team to the main Marvel Universe, where he met and fought the Avengers. His powers varied between just shifting his mass to other parts of his body to actual stretching. Given his limited mental capacity, it could be that his power is much more versatile than it appears.
7 Strongest: Thundra
Thundra has a long history in the Marvel Universe. Initially, she sought to best the Thing, proving that she matched his power. She became an ally of the Fantastic Four and proved her power many times against many foes.
She came to join the Squadron Supreme after they were betrayed by Warrior Woman, who had been impersonating Power Princess. She aided them in Weirdworld, and upon returning to Earth, she joined, if for no reason to determine if the world needed to be protected from the Squadron Supreme.
6 Weakest: Doctor Decibel
Doctor Decibel was one of the members of the Institute of Evil that underwent behavior modification and admitted into the Squadron. As a villain, he used sound-based weapons and was responsible for Lady Lark's powers.
As a member of the Squadron, he was primarily responsible for the medical needs of the team. He treated Hyperion's damaged eyes and Quagmire when he went comatose during a mission. He died when Quagmire's powers ran amok and drowned him in other dimensional muck.
5 Strongest: Power Princess
Power Princess is the Squadron's version of Wonder Woman. She's withstood blows from Hyperion and lifted immensely heavy items. She fought super-strong foes like Redstone. Her level of power commands instant respect from those that encounter her.
Even other versions of Power Princess have maintained this level of power. When the version of the Squadron consisting of refugees from around the multiverse was betrayed by Warrior Woman, she proved a match for almost every member of the team.
4 Weakest: Tom Thumb
Tom Thumb was the brains of the original Squadron Supreme. Initially, this was exhibited in the gadgets that he used. However, when the Squadron started their Utopia Program, his genius went to developing the means to change American society.
Creating the Behavior Modification machines, Non-lethal Pacifier Pistols, and personal force-field belts didn't leave him much time for physical development. After adding a progressive Cancer to the equation, it's not a surprise to see him counted among the weakest members of the Squadron Supreme.
3 Strongest: Redstone
Redstone was a mystery when he infiltrated the Squadron. He possessed great strength and yearned to test it against Hyperion. When Nighthawk's Redeemers forced a battle, Redstone quickly squared off with Hyperion. He held his own, with the help of his teammate Inertia preventing Hyperion's blows from affecting Redstone.
It was revealed that Redstone drew his power from the Earth itself. When he went with the Squadron into space, he lost not only his strength but significant mass. Even returning him to Earth couldn't save his life. While his counterpart in J. Michael Straczynski's Squadron Supreme didn't share this weakness, he did share his power.
2 Weakest: Moonglow
Moonglow's illusions were dependent on no one knowing that they were illusions. This covered up her lack of physical power. When her true form was revealed, she was shown to be very out of shape.
That revelation shows how weak she was. She was attacking Arcanna with the illusion of increased gravity, throwing her into labor. Arcanna countered with an illusion of her own. She then snuck behind Moonstone and knocked her unconscious with one punch.
1 Strongest: Hyperion
At different times, Hyperion has been an Eternal or an alien. All versions possess the immense power of the character Hyperion is based on, Superman. Hyperion regularly exhibits this power, yet seldomly cuts loose enough to show his true power. One time was when two versions squared off against one another.
His power is enough to guide a crashing space station through the atmosphere. The current version once held apart two merging Earths, gone up against the Hulk blow-for-blow, and lifted the city of Atlantis out of the water. It's no doubt that he tops the list of the most powerful members of the Squadron Supreme.