Thom

When Thom Creed initially signed-up for the try-outs of The League, he listed his hero name as simply "Thom". Later, over a moral quandary over another man being falsely accused of murder, he reveals his secret identity to the world.

Powers
Thom's powers are primarily healing-based. He is also able to sense anything he can heal.

He initially starts with healing physical injuries on plants, people, and presumably animals (though this never comes up), but soon develops the ability to sense and address deeper health issues, such as impending heart failure.

He eventually begins to be able to sense and negative emotions, such as heartache and panic.

By the end of the book, he potentially seems to be able to benefit from whatever he heals - either through immunity to it or utilizing it.

Consquences
While using his powers, Thom experiences a burning sensation in his hands that gets worse the worse the injury is.

Thom also has seizures as a byproduct of using his powers, which he can sometimes put off through a focused effort to relax himself.

Late-Stage Development
In Chapter 8 (during try-outs for The League) he's asked, "And what happens when you absorb the injury? [...] Where does all the pain go once you're done with the healing?" This seems to have been foreshadowing for future development for his powers.

In Chapter 33, after healing several crippling and life-threatening injuries in rapid succession, Thom discovers that he's able to transmute the energy absorbed from healing into powers. He then gains the powers of: super strength, super perception, and flight.