In your first encounter with Sandman, do not try to attack him, just stay close to him. Counter-attack him several times on different levels to finally battle him. Unfortunately, you must use the Black suit to damage him. Just hit him around until you are prompted to give him a bath. Keep doing this cycle until you defeat him.

Sandman will create a mini-tornado and you cannot hit him. Use your Spidey senses to dodge the flying bars and wait until he throws a tank at you. Press B when prompted and send it back at him, allowing you to beat him up. Do not get over-confident, as he will start up his tornado and do some damage. Repeat this until he dies.

The second battle with Sandman is very easy. Just dodge when your Spidey senses alert you and run to the yellow circles when they appear. Complete the prompts to throw TNT barrels into Sandman. Eventually Harry will kill him, ending Sandman.