in Omni-man vs Guardians, what was Nightwing's plan of attack?

seems it was like "i can use the speed generated by gravity to kick him extra hard in the head (extra hard by human standards)" or something? which, even if it had worked (which it didn't), seems completely pointless considering the durability of Omni-man.. what was he planning with that jump-attack? (*i've only seen the anime fight, haven't read the comic book)