Poor Jun. The goddess is so useless, she tells Graham she can't interfere anymore but that seems to also be her fault. If she just protected Jun or her reincarnation then the world wouldn't be at the brink of hitting it's limits. Even if we don't count Jun's misfortunes.
Making the succeeding heros forget also didn't do much but bring more harm to the world she claims to care about, because like the priestess said all the heros got devoured by the demon king and only made him stronger and also pushed the world closer to it's limits. Again this the dumbest goddess ever.
If she did sit around twiddling her thumbs and protected Jun, Marus would have arrived with the demon king's soul. Jun would have turned it back into a human soul and she could have been happy with Marus.
I really hope Lou can be happy this time.
But poor Marcus, I don't know if he can have a happy ending (there isn't a reverse harem tag). I mean the dude went and fought the demon king, only to come back to a dead Jun. All that hardship, all to help and protect Jun and his country. Only for his king, King Dumbass, and his countrymen to murder his beloved. That's just betrayal.