while lea experienced a few losses as axel, he eventually got them back in the end but i would say that losing roxas at first was definitely the most impactful. axel was first tasked with looking after him then they eventually hung out more and axel then started to feel emotion despite being a nobody. with xion’s disappearance, that made it somewhat more complicated because that’s when he lost grip of roxas altogether and left them at odds with one another for awhile. that definitely caused doubt in his own mind about what he really should be doing and yet– at the same time, axel wasn’t reckless enough that he’d overstep. you can definitely see how much that impacted him from there on out, doing everything in his power to make things right, some actions he even regretted. but if we’re also talking about something he lost as opposed to someone, i could say lea losing his heart and becoming a nobody after he and isa became apprentices of ansem’s then i could consider that being a big loss too, y’know.