Alpha Shapeshifter

"The king shapeshifter. First one who spawned all the others. There's tons of lore about it. -Samuel Campbell

The Alpha Shapeshifter was the very first shapeshifter.

Powers and Abilities
The Alpha Shapeshifter is an extremely powerful entity that is the father and leader of all shapeshifters. According to common lore, this Alpha has a connection or bond with its offspring which allows it to locate them.
 * Its strength greatly exceeds the strength of normal shapeshifters.
 * Its durability and threshold for pain are extremely high, and the only known material that can actually hurt it is iridium.
 * It can morph its body to match any human appearance. Unlike its children, it does not shed or peel while altering its shape.

Weaknesses

 * Iridium.
 * Decapitation.

6.02 Two And A Half Men
This shapeshifter starts gathering a following of its 'offspring' and is apparently reproducing with women by morphing into their husbands. When Sam and Dean rescue one of its children, the Alpha Shapeshifter storms the Campbell's compound and kills Mark Campbell, overcoming several gunshot wounds and tranquilizer darts, as well as a silver knife to the heart. It then reclaims the baby from Dean and leaves. This shapeshifter is able to transform in just a few seconds without shedding its skin.

6.10 Caged Heat
Crowley interrogates the Alpha Shapeshifter on purgatory's location. Crowley then reveals that iridium, although expensive and rare, is capable of damaging and killing the Alpha Shapeshifter. He threatens to kill the Shapeshifter's offspring that he currently has captured, but the Alpha Shapeshifter still refuses and tells Crowley that more shapeshifters would be produced if he killed the others. Crowley beheads the Alpha.