WARNING: This story includes mention of mass suicide, medically necessitated self-harm, and violence.
In an alternate timeline, word never got to Turnip's parents that the colonization would be taking place. In doing so, he was never sent to Earth. On the eve of his seventh birthday, the colonizers touched down. The Saiyans fought like hell against their tyrannical rule, but to no avail. Finally, they resorted to their ace in the hole: a full moon. The night came, and just as the moon was set to rise and turn the tides in their favor, they were met with a grave sight: someone had ratted out their plan, which led the colonizers to destroy the moon. With no other recourse, they did the one thing they could think of to retain the one thing they had left-- their pride. A mass suicide event ensued with the motto being "even in defeat, we claim victory", but one lone survivor remained. He ran. He ran until he found a secret bunker set aside for the royal family during destructive weather, but no royal family. There he remained all alone for thirteen years.
Being completely isolated for most of his formative years following such a traumatic event turned what remained of his mental faculties into that of a feral animal. At some point, he had to tear out his own eye due to an infection that he didn't know how to treat. His development was stunted and frozen in the mind of a child.
Eventually he was caught by the colonizers, but by that point he was beyond saving. He escaped containment after just a few hours and brutally tore out the throats of every single one of those alien bastards that he could find. Their leader was quick to leave in an escape pod before he could get to them, thus leaving them completely alone once again.