Adrien Walden

Adrien Walden is a former friend of Dane's who organised the graveyard party, where he also met Ezra. He is friendly and a good communicator. After the graveyard party, he meets Dane and Ezra in various other places. In the episode Every Second is a Lifetime it is revealed that he has been up to no good from the beginning, and in the end of the episode he shoots Ezra and leaves him for his his father to collect him.

In Season Two
Adrien appears as the primary antagonist, and recurs as part of the main story arch. He seeks Ezra for a stone artefact which he can do great evil with. According to the prophecy Tai-Gohng, should Adrien come in possession of this, one of Ezra's best friends will die.

It is unknown if Adrien's sadistic and inhuman nature is fuelled purely by his father's death, or whether he was already like this before, and his father's death intensified it, but it's likely a combination of the two.