Find a gooey mess of wreckage in the Man-Thing's swamp.
There's a cart of dynamite by the water's edge- push it to end of the track (with a toxic-immune character).
Your usual array of fire won't work here, but you can use a heatbeam to cut the gold bottom off a hanging cage.
These releases two chests, one of which is a monster. Smash both for the pieces to build a cannon.
No luck with the safe, but you can use the new pieces to build a green pump. Jump up and down on it a few time to raise a sunken helicopter.
Slice the vines away from the copter door to get the brick.