Hal Jordan from Green Lantern and Iron Man from Marvel would be a great team - up. Hal is a fearless test pilot turned Green Lantern, and Iron Man is a brilliant inventor. They could combine their skills in combat and technology. For example, Hal could use his ring constructs to assist Iron Man in creating new and more powerful armors, while Iron Man could help Hal upgrade his ring's capabilities with his advanced tech knowledge.
The Green Lantern Corps has several notable characters. For instance, Guy Gardner is known for his strong will and determination. Sinestro, although initially a member, later became a villain. Also, Alan Scott is one of the classic characters associated with the corps.
First, you need to understand the basic concepts of both Marvel and Green Lantern universes. For your OC (Original Character), think about their unique power set. Maybe it could be a combination of a Green Lantern's power ring abilities and a Marvel - like superpower, like Wolverine's healing factor. Design their backstory carefully, for example, they could be from a planet that has a connection to both universes.
One idea could be that the Green Lantern Corps discovers a threat that has its origin in the Marvel Universe, like a powerful artifact from Asgard that is being misused. The Green Lanterns then have to team up with the Avengers to retrieve and safeguard it. Another plot could involve a character like Hal Jordan being accidentally transported to the Marvel Universe and having to work with Spider - Man to find his way back home while also facing a common enemy.