He was, definetly, surely Mikoshi, being literally ripped apart by soulkiller and being able to dwell on his hatred for a long ass time didn't help, even Alt says he's not the same, his memory is warped and recollection of events are incorrect and bias.I think he was fucked up even before that ... since he came back from the war and all that...
I wonder if soulkiller that was used on him was the same that was used by Alt though, it has been updated probably hasn't it? Saburo was personally looking at the project.