The following are videos of all Boss fights and strategies to defeat them, as well as the endings.
Derrick The Executioner Boss Fight - Boss 1
Onryoki Boss Fight - Boss 2
Hino-enma Boss Fight - Boss 3
Nue Boss Fight - Boss 4
Tachibana Muneshige Boss Fight ("The Spirit Stone Slumbers" mission) - Boss 5
Tachibana Muneshige Boss Fight ("Invitation From The Warrior Of The West" mission) - Boss 6
Great Centipede Boss Fight - Boss 7
Umi-bozu Boss Fight - Boss 8
Marume Nagayoshi Boss Fight ("The Way Of The Warrior: Adept" mission) - Boss 9
Hattori Hanzo Boss Fight ("The Way Of The Ninja: Adept" mission) - Boss 10
Joro-Gumo Boss Fight - Boss 11
Yuki-onna Boss Fight - Boss 12
Onryoki Boss Fight ("Demon Hunting" mission) - Boss 13
Ii Naomasa Boss Fight - Boss 14
Nue Of Mount Hiei Boss Fight and Location - Boss 15
White Tiger Boss Fight - Boss 16
Giant Toad Boss Fight - Boss 17
Marume Nagayoshi Boss Fight ("The Way Of The Warrior: Veteran" mission) - Boss 18
Hattori Hanzo Boss Fight ("The Way Of The Ninja: Veteran" mission) - Boss 19
Onryoki Boss Fight ("Greater Demon Hunting" mission) - Boss 20
Ogress Boss Fight - Boss 21
Honda Tadakatsu Boss Fight - Boss 22
Okatsu Boss Fight - Boss 23
Giant Toad Boss Fight ("The Giant Frog Brawl" mission) - Boss 24
Honda Tadakatsu Boss Fight ("The Champion Of The East" mission) - Boss 25
Saika Magoichi Boss Fight - Boss 26
Hino-enma Boss Fight ("The Silent Crow" mission) - Boss 27
Otani Yoshitsugu Boss Fight - Boss 28
Shima Sakon Boss Fight - Boss 29
Gasha-dokuro Boss Fight - Boss 30
Saika Magoichi Boss Fight ("The Watcher In Darkness" mission) - Boss 31
Ishida Mitsunari Boss Fight - Boss 32
Obsidian Samurai Boss Fight - Boss 33
Oda Nobunaga Boss Fight - Boss 34
Kelley Boss Fight - Boss 35
Yagyu Sekishusai Boss Fight ("Sword Mystic Art Quest") - Boss 36
Ashikaga Yoshiteru Boss Fight ("Dual Swords Mystic Art Quest") - Boss 37
Hozoin Inei Boss Fight ("Spear Mystic Art Quest") - Boss 38
Sakata Kintoki Boss Fight ("Axe Mystic Art Quest") - Boss 39
Shisenin Kosen Boss Fight ("Kusarigama Mystic Art Quest") - Boss 40
Hidden Derrick The Executioner Boss
Yamata-no-Orochi Final Boss Fight and Game Ending
Hundred Eyes Boss Fight (Epilogue Endboss and Second Ending)
