The reason people from this world hate people that reincarnated or isekai is because a long time ago people from Earth tried to create a nation called 'Great Earth' (they have a coin as proof.)
The main character can detect other people's level (which is a trait for other worlders.)
The one that hunts the main character wears a helmet that blocks him from knowing his level.
Could this be Survival Story of a Sword King in a Fantasy World?
The description matches yours and there's repeated mention of "Great Earth" as a nation.
After untold years [of solo leveling], One day Hanbin is unexpectedly let out of his prison only to discover himself in a world that hates and fears him as an 'Otherworlder', a summoned being sent by the demon king to ravage the lands and slay the world's protecting Goddesses, with a long history of violence and bad blood between the Natives and the otherworlders like Hanbin. Forced to keep the truth of his identity secret, Hanbin must now find a way to survive in this strange new world without allowing others to find out his true identity, possibly get revenge on the beings who arbitrarily imprisoned him in a living hell against his will, and return to earth.
