How do I beat Rocksteady in the Genesis version of TMNT?

Answer 1

He is very strong, but very clumsy. Stand behind/below him and 
just slash away, but not for too long. Jump out of the way of 
his gunshots, and jump-kick him, but never twice in a row 
(he can counter-attack them).

Answer 2

Rocksteady is a fairly easy boss. If you're running low on health, then you'll also find a pizza on the same screen. Just save it for when / if you get into trouble.

Just jump over him everytime he charges, and smack him a few times.

And when he pulls out his gun, just make sure you're not standing in line with him and avoid the bullets as best you can.

Practice makes perfect. Just learn the rythme of this fight and it'll come easy!