I think 4th gen is the only generation to not have an offline only final boss, or even introduce an offline only monster at all. 1st gen had Monoblos, 2nd gen had Lunastra(I'm actually not 100% sure if she was the final boss of Dos, but she's still offline only at least), and 3rd gen had Ceadeus. I don't know what you would consider Cross' offline final boss(Dinovaldo from what I've heard?), but 4 and 4U had Shagaru and Rusted Kushala, but they're available online as well. Just something I noticed and felt like mentioning. I could be wrong because I might have missed one, in which case this post would be useless, but either way...uh...yeah.