I made it to the boss of the Chemical Plant island (finally!) and now I'm stuck (AGAIN). How do I kill this guy with unlimited girders and baseball bats while he's got the high ground and it's Sudden Death?

Any help would be awesome; thank you in advance!

There are several ways to complete this...

...I think the easiest is to box the hostile worm before you build stairs to the top of the map using the girders thus the enemy drowns before you.