Yeah we only got to see like 4 (Thats only how many i remember) out of 100 bosses not saying they should show all 100 but at least show like 20 or give some explanation to what happened to the other 96 bosses other than killed off screen and thats kind of how it is with every aspect of the Aincrad arc saying that the world is so big and there is so much to look foward to but then not showing anything