Perhaps there is no other person in the Dragon World with such a past as tragic as his. Future Trunks comes to us from a desolate world, ravaged by the cyborgs of Dr. Gero.
The son of Vegeta and Bulma, he was born with strength and power beyond that of any normal person on earth. Being of Saiyajin heritage meant that he had superior fighting abilities, especially when this bloodline is mixed with that of an earthling. With almost all of the rest of the warriors gone, Trunks trained with Son Gohan, who saw his power reach beyond a regular Saiyajin's level, and become a Super Saiyajin.
In Gohan, Trunks had a best friend, a training partner, a big brother... and a mentor. With him Trunks shared his thoughts, and their hopes for the future, when one day they finally annihilate the evil cyborgs, and finally bring peace once again to all the remaining people who have survived under the terror of these mechanical killers. An extremely heavy responsibility.
This responsibility grew even heavier as Son Gohan gets killed in battle with the cyborgs. Gohan, who knocked Trunks unconscious just before his final engagement with cyborgs, had known that if he was not to survive this encounter, Trunks would be earth's last remaining hope. However, having improved his fighting abilities, Trunks believed that had he not been unconscious, the outcome may have been different; this left Trunks with a great sense of helplessness, despair, and extreme sorrow... all of which he must bear at the tender age of 14.
Finally at the age of 17, in another battle with the cyborgs, Trunks realizes that his own powers are no match for the cyborgs, and heartily agrees to travel back in time, per his mother's wishes, to make contact with the one man she believes to be able to turn things around, a man who died of heart disease before the cyborgs showed up--Son Gokuu. This trip would not prove to be exceedingly worthwhile, at least from the perspective of Future Trunks. For although he does change the past, that past generates an entirely different timeline, having no effect on his own. Trunks returns again to the past about a year later, in the hopes of gaining some knowledge from Gokuu, or even to bring Gokuu back to the future with him, so that his world would be rid of the cyborgs.
During his second visit, he finds something much more disturbing. A creature named Cell. Fortunately, because of Vegeta and Gokuu's insights, Trunks was able to significantly improve his power, and because of the fight with Cell, he finds out that his father does have room in his heart for love. With this new found knowledge, Trunks returns eagerly to his mother, restoring peace on the earth, and making Trunks a more complete person, now knowing his father's love for him, and with the world's order restored, he no longer needed to live in sorrow.