u keep hitting him with the tnt barrels until the "chunky barrel" appears jump into it adn punch him using (z+b)once adn then just keep hitting 'A 'he wont fall into the lava until u have hit him 4 times being big adn if you punched him enough.

hit it with the TNT barrels the when the hunky chunky barrel appears get in it and start primeape punching it (Z+B) keep on doing that until chunky punches him into the wall

Start by pummeling him the way you defeated him before with diddy, use the tnt barrels to blow him up. then he's gonna jump and pound the thingamajig your standing on,but keep using the tnt barrels. then a chunky barrel will poof outta nowhere so jump in then kick the bosses butt! (YOU HAVE TO DO THIS A FEW TIMES IN ORDER TO DEFEAT HIM, SO ACT QUICKLY OR ELSE THE LAVA WILL KILL YOU!)
I reccomend you use Z+B when you are big.

This boss has a few new tricks, but chunky can get big!

The old fireball attack again. Keep junking to stay out of range. The splash of fire is damaging for a few seconds. After that time, chunky can run safely through the wide ring of fire left behind. The boss can rock the world with a slam. If you can, jump over the wave, grab the TNT barrel and throw it at him. A FIRE WALL!!!!!! Backflip as fast as you can as the timing is hard for this one. After a while, the boss jumps onto the battle arena and starts to sink into the lava. After dodging the fire balls again, throw the TNT barrel. A chunky barrel appears. Jump in and primate punch the boss Just start primate punching when the huge chunky appears. After a few punches, you have earned K.Lumsy's key.

I forget.

you have to jumo into the fire with big kong 6 times..... seeya