Megaman ZX (Aile/Hard/No Damage) - Part 11: Fight the Irregulars [Fistleo] 

At 5:15, my inner self was screaming desperately. That was SO CLOSE, you can see how that affect me. After that few bullets miraculousy dodged, I went full defensive/cautious mode my way to the boss.
This stage is hard, if you try to pass through it relying only with Model ZX... I can only wish good luck to you. This is one of the cases that I have to use other megaman form in order to not lose my patience and to make things easier for me.
Here, lies the most difficult jumps I've ever seen in a plataforming/2D game. Thankfully, the game gives you Model HX and Model PX (Hello, Shadow Dash), both can pass easily through the flames, but the last one recquires weapon energy. Thus, making Model Hx exceptional to pass the fire untouched without any costs.
This boss is cheap & dump. Really, whoever got the idea to put his head as his weakness is a BIG ************. But that's not really the big trouble... this boss' hitboxes are bugged. Sometimes you'll hit his feet or his back and the game will count as "Livemetal Damage".
If all this wasn't bad enough... he can also heal himself. While you barely attack'im fearing to damage the livemetal inside of this beast.
I prepared myself to kill him using only Model ZX. Being the best form if the game, it can deal with him or every boss, very well. Unfortunately, there's no way to abuse saber slash or charged shot. There's just few moments in battle were you can attack with 100% conviction that it'll not damage Model F... and this excessive caution will make him heal from every scratch you've done through the battle...
So luck play a big part in a level 4 finish. Thankfully, Meta_X made a video killing every boss using only Model PX. I remembered about his video, watched it a few times, and used overdrive to boost kunai's damage. I kinda tried to use Model PX like him, but his skills are supreme hahaha
There is other way to kill Fistleo quickly? Yes. Use Model HX overdrive (one full combo is enough to kill him) or use Model X (that should be selectable after getting Model Z 👀).