The Incredible Hulk #110

Ka-Zar and the Hulk battle as the jungle lord tries to figure out a way to get him to turn back into Bruce Banner in time to stop an alien machine from destroying the earth using deadly weather patterns. Ka-Zar is captured and taken by the Swamp Men to be a human sacrifice for the giant creature known as Umbu. Hulk fights Umbu but transforms back into Banner thanks to a fortuitous gas attack. Banner races to stop the mysterious earth destroying machine with Umbu close on his tail and trying to stop him. Banner succeeds but is killed in achieving his victory.