Gamora

Origin

The Zen Whoberi was a population who were wiped out by Badoon. (However in the original storyline they were killed by the Universal Church of Truth.) Gamora was the only one of the Zen Whoberi that survived.

Thanos discovered Gamora alive and decided to train her as a weapon. Thanos wanted to kill the Magus who were evil and Thanos planed to raise and train Gamora to do the job. Thanos made sure Gamora was raised with discipline and he did not show her any affection as a father would show his child. This did not matter to Gamora because her desire was to take revenge on the one responsible for the death of her family and Thanos would provide her that opportunity. Therefore she trained very hard and became a master of the martial arts.

Even though Gamora was learning and becoming a master martial artist she still had more to learn. She went on a trip with Thanos and she got into a fight with a group of thugs that were able to defeat her in spite of her great skill. She was injured in the fight and when Thanos found her he helped her regain her heath cybernetically. This increased her power to superhuman intensity.

When Gamora grew to adulthood it was time for her to begin the mission she had trained for all her life, to go after Magus and the Universal Church of the Truth. Her abilities and skill made her a dreaded assassin. She was able to get close to Magus but failed in her assassination attempt. She had others with her in her attempt and all of them had to fight to escape the Universal Church of Truth. These others were Warlock, Pip the Troll and Thanos. Even though this attempt failed in due course the Magus was defeated. It was after this that it was discovered that Thanos was even more evil and dangerous than the Magus. Some time later, Gamora was piloting a space ship when the ship came under attack from Drax the Destroyer, whose sole purpose in life was to destroy Thanos.  Drax had targeted Gamora's ship due to her relationship to Thanos and destroyed the ship.  As Gamora lay dying, her ally Adam Warlock was able to take her soul into his Soul Gem.

Soulworld existed inside the Soul Gem. This was where Gamora, Pip the Troll and eventually Adam Warlock existed in peace. Years later, when Thanos returns from the dead, Soul World is visited by the Silver Surfer and Drax the Destroyer, who are there seeking aide from Adam Warlock who had destroyed Thanos before. Finally Adam Warlock determined that Thanos must not be not permitted to continue to grow in power. Warlock guided his allies Gamora and Pip the Troll out of their peaceful Soulworld to the real world. When they entered the real world they needed bodies to exist in so their souls took over the bodies of three people that had died in a car accident. In the following struggle Thanos did away with half the population of the universe, including Gamora. When Thanos was defeated Gamora returned to existence.

Infinity Watch

At the end of the Infinity Gauntlet ordeal, Adam Warlock was in possession of all six infinity gems but by order of the Living Tribunal was unable to use them together, so Warlock gave all but the soul gem away to guardians he trusted and called this group the Infinity Watch.  Gamora was brought on board as guardian of the Time Gem; a power that Gamora didn't really want and had no idea what to do with; though almost as soon as the gem was on her brow she experienced a premonition of Warlock being killed by an unfamiliar figure who would later be revealed to be future Infinity Watch member Maxam. 

During her time with the Infinity Watch Gamora began to have romantic feelings for Adam. At first Adam did not feel the same way but after some time Adam began to feel the same.  

During "The Infinity Crusade" Gamora was chosen as one of the Goddess' highest ranking servants as a member of the Holy Guard.  Goddess used her own personal beliefs and telepathy to control Gamora to help her create a group consciousness across the universe and rid it of evil. When the battle with Earth's heroes on Paradise Omega, Gamora proved that she was more than enough for some of Earth's mightiest heroes able to take out Rage as well as the Thing. She was stabbed in the stomach by Wolverine, but her healing factor eventually revived and healed her. The control over Gamora was eventually released and the Goddess was defeated.

Personal issues as well as her fears about Maxam once he arrived and befriended the Watch drove Gamora to leave the team and abandon the Time Gem, which Warlock in turn gave to Maxam.  She would come back to the team in the end just before the gems all vanished and the team dissolved.

After the Watch

Later, during the "Infinity Abyss" story, Gamora and Adam would raise a cosmic being that was known as Atleza.

Some time after this, Gamora is present with Adam Warlock and Pip the Troll on a planet that has been taken over by the Champion of the Universe.  Warlock is gathering the universe's strongest heroes to combat Champion in the ring as if anybody can beat him he will relinquish his rule over this world.  Warlock's initial recruits: Beta Ray Bill, Drax the Destroyer, Gladiator, The Silver Surfer and Warlock himself all fail.  Next, Warlock sends Pip out to retrieve She-Hulk who Gamora serves as personal trainer for to combat Guardian.  She-Hulk loses to Guardian in her first fight with him but is awarded a rematch when she points out that Champion, who has regained the Power Gem, was using an illegal weapon to boost his prowess.  While waiting for the rematch, Gamora convinces She-Hulk to train for the fight in her human form rather than as She-Hulk, as while She-Hulk her human strength becomes exponentially multiplied, so if she is stronger in her human form then her She-Hulk form will have greater strength still.  Gamora's insight paid off, as now-buff Jennifer Walters makes She-Hulk stronger than ever and she beats Champion with ease.

At some as-of-now undisclosed time, Gamora left Adam and Atleza to go off on her own to try to reclaim her title as Deadliest Woman in the Universe.  She sets herself up with a new costume and a new weapon, the dagger known as Godslayer, upon a fringe Kree colony as head of "The Graces", a group of super powered female characters, mostly villains, consisting of Nebula, Cerise of the Sh'iar, Tana Nile, Spirit and Stellaris the Celestial Slayer.  This is at the start of the first Annihlation war, and Gamora is drawn into conflict with Ronan the Accuser who is trying to track down one of her graces, Tana Nile, who had testified against him in court on false charges that had left him disgraced.  Gamora and Ronan battled to a standstill and eventually joined forces against t he Annihilation Wave, and both joined Nova's United Front.  During her time fighting alongside the United Front, Gamora strikes up a romantic relationship with Nova.  When/why/how she fell out with Warlock before that remains to be shown.

Between Annihilation Wars, Nova apparently broke off his relationship with Gamora, but this is also "off panel".  During the second Annihilation War, Gamora is taken over by the Phalanx and is turned into one of their Select.  As a select, Gamora is critical in apprehending and infecting Nova and Drax the Destroyer.  Nova manages to free himself from Phalanx control, only to immediately be pursued by select Gamora and Drax.  They follow Nova to the current home world of the Phalanx' parent species the Technarx, where Warlock (former New Mutants member Warlock, not Adam Warlock) manages to free Gamora and Drax from phalanx control.

After the second Annihilation war, Gamora joins Peter Quill / Starlord's new incarnation of the Guardians of the Galaxy.

Powers

Gamora’s martial artist skills are considered to be among the highest in the Marvel Universe as she has mastered 83.4% of most known armed and unarmed techniques from various warfaring cultures. She can defeat opponents who are stronger than her. Her skill gives her the ability to outfight others who would be considered more powerful. She even defeated a whole platoon of highly trained military personal in a short time. She has the ability to paralyze or kill opponents by striking vital nerve cluster points on their bodies. Her preferred weapons are swords and knives.

Most of Gamora's skeleton has been replaced with a nearly unbreakable substance by Thanos.