Clingy Costume: As an astronaut in an experimental sublight journey to Alpha Centauri, he was put inside a copper-lined uniform to survive a thousand-year space journey. If it is ever pierced in any way, he will suddenly age a thousand years.
Exposed Extraterrestrials: He’s a crystalline transhuman from the planet Pluto. His body is composed entirely of crystal, and never wears clothes.* GadgeteerGenius Bruiser: He possesses enhanced strength, speed, and stamina as well as having earned doctorates in physics and engineering.
The One Who Knows: Advised the Guardians on what course of action to take. This wasn’t a superpower, it was Stakar stuck in a time loop where he always relives his life from infancy, knowing what to do from experience.
Deus Exit Machina: Generally regarded as the team's heaviest hitter, Groot was absent from the team's official foundation as he was still recovering from his sacrifice in Annihilation. Likewise, whenever he needs to be written out for drama they simply have him make a slow recovery from a prior battle.
Glass Cannon: So far, he got smashed to pieces in Bendis stories a bit too easily.
Healing Factor / From A Single Splinter: A very impressive one. Groot can, depending on the circumstances, regenerate lost limbs and even his entire body within seconds of being destroyed. Though going from a single splinter usually takes much longer and requires water.
Bad Ass: Fought Norman Osborn's Thunderbolts team after violating the Superhuman Registration Act, and only lost because Bullseye stabbed him the spine, leaving him paralysed.
Handicapped Bad Ass: Even whilst in wheelchair, Jack became the de-facto leader of the inmates of Prison 42 after the wardens abandoned the prison during the Secret Invasion & fought off Blastaar's forces in his attempt to gain access to the prison's portal to Earth.
Only Sane Man: Prior to joining the Guardians, Jack was imprisoned in Prison 42 located in the Negative Zone, for breaching the Superhuman Registration Act. When he joined up with the Guardians, he reacted to most of the cosmic stuff with "I hate cosmic stuff" due to his background as a street faring vigilante.
Throwing Off the Disability: Left paralysed from the waist down following his run in with the Thunderbolts. The damage to his spine was healed using alien technology during his first visit to Knowhere.