I think out of the Green Lanterns guarding Earth, either Hal Jordan or John Stewart would definite suffice and as for Aquaman, like the idea of him summoning water so his marine friends (fish, turtles, sharks, fellow Atlanteans, etc.) can attack the opponent whilst underwater. And let him keep the facial hair.
I still remember how Black Adam eradicated the area in DC Universe Online intro (the lightning when he yelled "Shazam!!", Green Lantern's power ring and Flash's speed combined caused a catastrophic explosion, killing Green Lantern, Flash, Cyborg, and Harley Quinn; plus, putting the heroes in a very losing situation).