Bukaro
with tengen toppa gurren lagann can fight most of the multiverse if not all alone, i don't see what difficulty he can have
yes also level toaru and OP, however if you can try to send MC to some storyline with the world without additional storylines, if you can try to send him to worlds where he can make subordinates or OP powers, he could go to medaka box and he could make friends medaka and ajimu (even though he has full arsenal he doesn't seem to be able to leave his world you can do like it is a world within the book written by a powerful one or something), this could help mc because he is going towards fairytail power (check the fairy tale as the author or see everything as a narrator)
Yuuki_Kyouya:Yep Mondaiji Top tier is Op
Author I find some people that need human shaped man Vivarator to satisfy his harem. Luis should give some advice to mc who is a system user to the core that he (Luis) doesn't need a human shaped Vivarator to satisfy his harem. Maybe Navi is enough to fix him "Hey Listen I know that you're a pathetic loser who has Micro pe**s is not enough to satisfy your harem. So you start creating human shaped Vivarators so that you can hide your pathetic self. So you should leave your women and Harem king show you how to satisfy women"
aha! so, there is a chance that servants will show up. have you thought about introducing china-based servants like Qin shi huang, sanzang? it will be dope! looking forward to epic clash of noble phantasms. I will start fanboying now thinking about future Excalibur with sword of promised victory bgm!