Alex Volkov is a devil blessed with the face of an angel and cursed with a past he can't escape. Driven by a tragedy and vengeance that has haunted him for most of his life, his ruthless pursuits for success and vengeance leave little room for matters of the heart.

Cold, trust issues, heartless, protective 

Jace has a strong moral core. He is dutiful and just, willing to make the right decisions, and sacrifices if it comes down to it. Though he can be, at times, vindictive, he is cruel only to protect those he loves. No one can see Jace except Shadowhunters 

Arrogant, protective, cocky

Doom as his name, is the literal meaning of Doom. He's the deity of Doom. He can make things die, stop working or even suffer.  

Cruel, selfish, unable to love, teases a lot, 

I'm fair to everyone. Except her. She's the one that makes me nervous and I'm never nervous! I'm a surgeon and she's an ER doctor

Cold, protective, justice, tough

He is a demoted detective who has begrudgingly spent the last year on the maritime unit. 