Ninja Gaiden 4 contains 20 bosses. This guide shows all boss fights on Master Ninja, which is the hardest difficulty. You must beat the game on Master Ninja difficulty for the Way of the Master Ninja trophy & achievement.
Below are videos for all bosses sorted chronologically by chapter.
Chapter 1: D.D.O. Commander
Chapter 2: D.D.O. Proto-Goliath
Chapter 3: Kitsune Courtesan
Chapter 5: Sanzeon
Chapter 7: Kurobo
Chapter 9: Veilotl
Chapter 10: Cetus
Chapter 11: D-1018 Chario
Chapter 12: Elevator Fight D.D.O. Commander
Chapter 12: D.D.O. Proto-Goliath
Chapter 13: Kagachi
Chapter 13: Achilles
Chapter 14: Achilles
Chapter 15: Cetus
Chapter 16: Kitsune Courtesan
Chapter 17: Kurobo
Chapter 18: Totyos
Chapter 19: Ryu
Chapter 19: Dark Dragon
Chapter 19: Dark Dragon (Phantom Form)
That’s all bosses in Ninja Gaiden 4. For more guides refer to the Ninja Gaiden 4 Guide.