(So the situation involved not merely child abuse and enhancement, but human experimentation... after all, I see no reason why only one soldier would be made immortal deliberately.)

So it's highly likely that... [...yawn...] ...that Albedo is among the more dangerous kidnappees here, even under normal circumstances. However, if he and Gaignun were both raised under such conditions, explaining Albedo's instability would seem to tell only half the story.