Alpha Shapeshifter

The Alpha Shapeshifter was the very first shapeshifter and the one who spawned all the others.

Early Life
He was the first Shapeshifter created by Eve. Exactly how old he is is unclear, but as the stories of his children are thousands of years old, it is likely he has been around since his mother last walked the earth, ten thousand years ago.

Season 6
In "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.

In "Caged Heat", Crowley interrogates the Alpha Shapeshifter on purgatory's location. Crowley then reveals that iridium, although expensive (saying that dropping a castle on him would be cheaper) 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.

Powers and Abilities
The Alpha Shapeshifter has all the traits and abilities of normal shapeshifters, although at unbelievable levels. It also has several unique powers, which come with being an alpha.
 * Shapeshifting - It can morph its body to match any human appearance. Unlike its children, it does not shed or peel off its skin while altering its shape. It can change its form in seconds and it can also copy clothing. His shapeshifting ability was such that it was akin to shapeshifting of stronger beings like Eve and the Leviathans.
 * Supernatural Strength - Its strength is monumental compared to that of all other shapeshifters, being able to overpower four hunters simultaneously, lift a grown man into the air with one hand, and rip a solid iron door off its hinges.
 * Regeneration - Able to heal wounds caused by knifes and bullets incredibly quickly.
 * Immortality - He can live forever, provided he isn't killed by decapitation or iridium.

Alpha Abilities

 * Enhanced Endurance - Its durability and threshold for pain are extremely high, being only susceptible to iridium, though decapitation works too. According to Samuel, the Alpha merely chuckled when shot with an elephant tranquilizer.
 * Immunity - Unlike lesser Shapeshifters, the Alpha is immune to silver.
 * Telepathy - Like all Alphas, he has a telepathic link to his children, thus allowing him to locate them, regardless of where they are.

Weaknesses

 * Iridium
 * Decapitation

Trivia

 * The Alpha Shapeshifter is the first Alpha to be killed in the series.