AStoryForOne
He needs to go to a place where planetary busters are normal. Take him to Dragon Ball Z, Toriko, One Punch Man, Marvel, DC, JoJo, Jujutsu Kaisen (not planet level but still has some things useful to MC, could help him get reality marble), Naruto (for senjutsu, I doubt Goetia can manipulate that like he can magic, plus this would be good for Yasaka and their daughter), The Misfit of Demon King Academy (some very broken things he could learn from Anos), Hunter X Hunter (all get their own abilities and are only limited by their imagination and amount of Nen which would be nothing for the MC), That Time I Got Reincarnated as a Slime (not sure how much he could gain here besides some unique skills and magic but he might be able to become a demon lord and get a boost), One Piece (Haki is quite versatile and some of the fruits there have really broken abilities). Or he could just go back to Campione and kill more gods to gain more authorities.