Klaus Hargreeves (Number 4)
Klaus’s abilities enabled him (or perhaps forced him more precisely) to communicate with the dead. After being repeatedly traumatized by his father’s experiments to push him to his limits, including locking him in mausoleums for days surrounded by ghosts, Klaus went completely off the rails. On his own, he became a drug addicted alcoholic, caught in a seemingly endless downward spiral, all while presenting a flamboyant and narcissistic front.
During season 1, Klaus accidentally traveled back in time to the Vietnam War, where he met and fell in love with an American soldier named Dave. Dave tragically died in battle and when Klaus returned to the present he kept Dave’s nameplates. Now dealing with post-traumatic stress, Klaus tried to clean himself up.
The other major revelation for Klaus in Season 1 was that Ben, his brother who had been killed on a mission during his childhood, is actually still present as a ghost that only Klaus can see and communicate with.