Triplicate Girl was certainly unlucky pre-boot - and it never occurred to me that of course you'd buy three action figures of her!
Even Triad, this time around, had an awful childhood then got beaten severely by the White Triangle.
Lightning Lad is perennially unlucky - all versions. Maybe his luck is about to change? Wonder why he's the character always losing his arm, dying, etc etc?
I would also add Brainiac 5 - his childhood is usually depicted as unpleasant if not miserable; he kept losing Supergirl, he lost Andromeda (two versions), he can't seem to lose Computo in any version and his grand experiments tend to be 50:50 disasters:successes. At least he's still alive, so I won't call him the unluckiest.