This is in level 1-12. When the fight starts, he will run into the wall above 3 times and then drop down to run at you. Double jump to get over him so he hits the wall and jump on his head when he isn't moving. When he starts the tornado attack, use double jumps to keep him from hitting you. After jumping 3 times, you can jump on his head again and he will then go back to the place above you. He will then run into the wall 5 times before dropping back down to where you are where you will do a repeat of double jumping, hitting him on the head when he isn't moving, and having to jump his tornado attack 5 times. The third (and final) round, he runs into the wall 7 times before dropping backing down to you and you do the repeat of the same process but you will have to double jump his tornado attack 7 times. The walls get shorter after every round so the jumping has to be done quicker each round. I found it easier staying against the right wall when the thorns are dropping and counting him hitting the wall the 3, 5 and 7 times so I knew to expect him to drop down and move from the final thorns that would fall (usually above the character). The thorn attacks are random and somewhat frustrating but counting the wall hits when he was on top really helped me get past this part.