Shocked! Villains from the Reader's Perspective

These questions about villains came in at the end of July and the beginning of August:

First from JesseGee: I have a character in my book named Garrett. At the end of my story, he will betray his family and friends by trying to kill my main character for the queen, an evil woman who wants to annihilate his kind (which he knows) but needs his help to do it. I have put bits into my story that will help his betrayal in the end make more sense, but, purposely, I haven't yet made it clear if he is...