Reverend Levon James - Unknown
Kerry Wiebe - Unknown
Bartal Gulyas - Unknown
Ellie Fantone - Unknown
Gustav Gattis - Unknown
Mikael Woltorf - Enemy Number One mission, Old Quarter map, found in the northern rooftop area as part of the leaping swarm
Agra-Ek - Unknown
Raymundo Carlos Pena - Unknown
Klaus Gervasius - Unknown
Armand Efinst - Unknown
Captain Rowner - Unknown
Bishop - Unknown
Detective Reinhart - No Way Out mission, Market Subway map, found near the end of the main pathway a few rooms from the boss room
Freddy Williams - Unknown
Gustav Renden - Unknown
Jameson Kirch - Unknown
John Fitzgerald - Unknown
Loris Asanhi - Unknown
Paul Hastings - Descent Into Darkness mission, Market Subway map, found towards the middle of the main pathway
Thomas Wilfried - Unknown
Szandor Hagen - Uknown
Captain Metzger - Unknown
Eli Holden - Unknown
Doctor Gottschalk - Unknown

Please reply if you have encountered one of the minibosses above that I have not yet and I will update this OP.