Alec is clearly a Shapeshifter. He started out his run on the show as irreverent, careless, and as Logan put it, a "happy go-lucky sociopathy". He thought only of himself and only worried about something if it directly involved him or impacted him in some way. After being unchained from Manticore and swept up into Max's circle, he was put through a crash course in how to be a better person, always held to the standards Max set for him. His relationship with Max is what shaped him and changed him from the think-for-yourself he had been, into the man who readily put himself in harm's way for those he cares about.
The other clear choice for him would be the Trickster. Alec was an obvious device for comic relief (though Joshua shared the role with him) and mischief.