This is my fan theory and it may or may not be true.
Zachary Levi's character Luke Collins, has a power that will be familiar to fans of OG Heroes. He has nuclear power, who remembers Ted Sprague from season 1 of OG HEROES? The man who boiled water in a glass?Look familiar?Now there were two Characters that had this power after Ted dies, Sylar and Peter. now here is my fan theory;Luke is Sylar.
When Luke returns to his house in episode 4 of Reborn, he is wearing a dark jacket and hat. Remember Sylars favorite outfit for hunting EVO'S?Same outfit.Now we have seen Sylar live for an extended period of time as another person, when he became Nathan Patrelli. But that was done by Matt Parkman who was still a novice in using his powers.
So what if an experienced mind manipulating EVO did it this time around, the Haitian or Casper perhaps? Now why would Sylar do this? Well in the final episode of OG Heroes we see Sylar become the hero and the last words we here him say ever is "Everything is going to change" What if Sylar didn't want his powers anymore or the memories of killing so many of his kind? And he becomes another person, he falls in love and has a kid, similar to the episode in OG Heroes when a future Sylar is docile and has a son. And what happens when his son is killed? Sylar goes nuclear.
Why do his powers start to come back? Well in the final season of OG Heroes Robert Knepper played Samuel Sulivan an EVO whos powers were magnified by being in close proximity to other Evo's. By the end of the show Sylar could take power by just a touch, he shook Samuels hand. So in Reborn by killing so many Evo's and since energy is never created or destroyed, energy bit by bit latched itself onto Luke and built up untill his powers started to manifest again.And just for fun, i don't think it's a coincidence that Tim Kring cast another actor that has a constant 5 O'Clock shadow, black hair, thick eyebrows and cut his hair with a high fade. And they are both named Zachary.
Or this could all be my own apophenia.