What if Batman kept the Yellow Power Ring? Preparing to level the playing field between himself and super beings, Batman would train immensely to become one with the power ring. Creating a physic link (conscious and subconsciously) with the ring will allow it to instantaneously connect to Batman when facing a super being, cutting out the time it takes putting it on manually. If such a battle took place, Spawn would be totally outmatched by a Sinestro Corps Batman.
Instead of battling, it would be advantageous to team up as show in the comic book. Spawn’s costume works similar a lantern ring in the effect that he could shape shift his armor with concentrated willpower. Just imagine if Spawn was apart of the Black Lantern Corps? What do you think the outcome would be then? Spawn could use the ring to enhance or merge it with his necroplasmic power making him a completely new being. Since Spawn freed his soul and transformed to an angelic form, would that mean he would also become recruited into the White Lantern Corps?
Heroes will battle each other to discover strength and weaknesses, but eventually team up to serve a bigger purpose than themselves. Just imagine if a crossover film were produced with the Sinestro Corps Batman and Spawn, giving the fans an idea of how Batman would use such power. So far, the Sinestro corps Batman has reached into video games and toys, why not film?
Since Batman refused the yellow lantern ring, do you think Nightwing would refuse such power? Maybe not….