Ali Larter / Niki Sanders/ Tracy Strauss / Heroes

Nikki Sanders

Ali Larter has appeared on the television series Heroes as not one, but two different characters.
Well almost three.
Ali started out as Nicole "Niki" Sanders and "Jessica".
And oh yeah.."Gina", so I guess that makes four....
Anyway, Nikki suffered from split personalities. Jessica (the one with all the powers) emerged first and Gina was shown in the Heroes episode "Four Months Ago...".
Nikki/Jessica possessed enhanced strength and increased physical durability.
And Jessica possessed a mean streak a mile wide.

Jessica Sanders

Unlike most of the other Heroes, Nikki was given her powers by Dr. Zimmerman.
Nikki's final episode was "Powerless".

Tracy Strauss

And that leads us to Tracy Strauss, Tracy is the triplet sister of Nikki.
Triplet?
Okay...there's another sister Barbara.
So that brings Ali up to five roles.
That's assuming Barbara and Tracy don't have split personalities.

Anyway, Tracy has the ability to freeze anything that she touches.
Or in fancier terms,she can reduce the kinetic energy of atoms and thus reduce temperature.

And if the writers ever get tired of Tracy, they always have Barbara.....
She hasn't been shown physically on the series (that we know of).
But there is a really good discussion page at http://heroeswiki.com/Theory:Barbara with fan theories about Barbara.