Vega 2 is Vega's temporary replacement, while Vega got repaired. She is programmed to destroy all heroes. Vega has a mind of her own, but Vega 2 is an actual robot! Misty and Tech Mitter made Vega 2. Vega 2 is still played by Thora Birch but Vega 2 has more of a robotic voice then her.
In other words, Vega 2 is actually more evil then Vega, but never made it to The Top Villains of the Year. Vega X was going to destroy Vega 2 and Vega and replace them with herself but, it is too complicated.