Hello, yes, you need a flash the boss N times. His assistants can be killed with a gun or you can just ignore them and run away.

This end boss is stupid difficult, iv just spent almost 2 hours without completing it. You dont have enough health/stamina/flash to win, almost but not quite. Skill goes out the window here, too much luck involved. Maybe if you get lucky and he gets stuck in the map a couple of times.. You gotta fix that sh*t, any enjoyment is ruined by the tediousness of the end boss.

Glitch trick I just learned beating this tonight. And believe me, this fight took longer than anything else I did in the game. If you shoot the sidemen before engaging the boss cutscene, you CAN kill them and just go 1 on one with the boss with less to worry about. It's still a horrible fight though with 2 flashes. I barely scraped through by the skin of my teeth. But that's the bit of help I can offer through extreme trial and error.