This guide will explain how to beat Olmec, but will not detail how to get there.
How to Beat Olmec
Beginning the Fight
In the beginning of the fight Olmec will be in the center of the arena, and will bounce towards you, note that crushing you is his ONLY way of killing you, he will bounce rather slowly and deals no contact damage.
When you begin the fight you should head upwards to the top of the arena using ropes, climbing gloves or a jet pack. There are multiple crates and assortments of treasure up there, I recommend collecting as much as you can, especially the crates because you need at least 7 bombs to beat the fight. There might also be a character coffin up there, so grab that for an exclusive character.
The Middle of The Fight
Once you're done collecting what you need at the top of the arena, go back down to Olmec, and jump on his head (him? he is only a head so ig). Once you're on Olmec move to the left of him, and let him jump around and move him to the left side of the room and run away, he will only jump at you when he is on screen.
Once you do that bomb a tunnel going downwards, this tunnel will lead to the lava, which is the only way to kill him. The tunnel needs to be 4 tiles wide, which requires you to bomb in the same spot, one at a time and lastly at the corners, straight down. Once the corner bombs are placed leave the tunnel ASAP. There is no urgency in this other than the bombs, so you can hang there for a bit to catch your breath and calm down, or do whatever.
The End of The Fight
After you've left the bomb tunnel, head back over to Olmec and lead him to the bomb hole, he will start jumping towards you and by the time you reach the tunnel, stand on the edge of it, but don't trigger the animation when you are on the edge of something. Olmec will jump at you, detect you under him, and when he stops in the air move out of the way and he will fall straight to his death. Once Olmec is in the lava, the door on the far right side of the arena will open, you can then use the door to trigger the end sequence and beat the game!