Death Battles by Time

The Death Battles that have happened are the ones that happened when they start at the beginning (after the analysis, and most of the times a sponsor of the episode) and conclude with a victor (most of the time), here they are in that order:

Season 1
Episode 1. Boba Fett VS Samus Aran (1:18)

Episode 2. Akuma VS Shang Tsung (1:16)

Episode 3. Rogue VS Wonder Woman (1:15)

Episode 4. Goomba VS Koopa (2:00)

Episode 5. Haggar VS Zangief (1:24)

Episode 6. Teenage Mutant Ninja Turtles Battle Royale (1:32)

Episode 7. Zitz VS Leonardo (0:57)

Episode 8. Yoshi VS Riptor (0:55)

Episode 9. Felicia VS Taokaka (1:37)

Episode 10. Kratos VS Spawn (1:16)

Episode 11. Bomberman VS Dig Dug (1:03)

Episode 12. Vegeta VS Shadow (2:05)

Episode 13. Mario VS Sonic (3:09)

Episode 14. Justin Bieber VS Rebecca Black (1:37)

Episode 15. Luke Skywalker VS Harry Potter (1:26)

Episode 16. Chun-Li VS Mai Shiranui (0:57)

Episode 17. Starscream VS Rainbow Dash (2:56)

Episode 18. Master Chief VS Doomguy (1:35)

Episode 19. Eggman VS Wily (5:07)

Episode 20. Zelda VS Peach (1:48)

Episode 21. Thor VS Raiden (2:37)

Episode 22. Link VS Cloud (1:47)

Episode 23. Batman VS Spider-Man (1:50)

Episode 24. Pikachu VS Blanka (1:11)

Episode 25. Goku VS Superman (10:29)

Season 2
Episode 26. He-Man VS Lion-O (4:19)

Episode 27. Shao Kahn VS M. Bison (2:15)

Episode 28. Ryu Hayabusa VS Strider Hiryu (1:59)

Episode 29. Ivy VS Orchid (1:14)

Episode 30. Fox VS Bucky (2:41)

Episode 31. Terminator VS RoboCop (7:36)

Episode 32. Luigi VS Tails (3:00)

Episode 33. Pokémon Battle Royale (3:06)

Episode 34. Fulgore VS Sektor (1:12)

Episode 35. Godzilla VS Gamera (6:34)

Episode 36. Batman VS Captain America (1:32)

Episode 37. Tigerzord VS Gundam Epyon (5:10)

Episode 38. Ryu VS Scorpion (3:33)

Episode 39. Deadpool VS Deathstroke (6:34)

Episode 40. Kirby VS Majin Buu (6:00)

Episode 41. Ragna VS Sol Badguy (2:32)

Episode 42. Gaara VS Toph (3:55)

Episode 43. Boba Fett VS Samus Aran Remastered (3:24)

Episode 44. Chuck Norris VS Segata Sanshiro (3:01)

Episode 45. Guts VS Nightmare (3:17)

Episode 46. Iron Man VS Lex Luthor (6:59)

Episode 47. Beast VS Goliath (1:48)

Episode 48: Solid Snake VS Sam Fisher (7:30)

Episode 49: Darth Vader VS Doctor Doom (3:30)

Episode 50: Goku VS Superman 2 (6:21)

Episode 51: Donkey Kong VS Knuckles (3:29)

Episode 52: Wolverine VS Raiden (4:16)

Episode 53: Hercule Satan VS Dan Hibiki (6:37)

Episode 54: Yang VS Tifa  (3:27)

Episode 55: Mega Man VS Astro Boy (3:46)

Episode 56: Green Arrow VS Hawkeye (3:04)

Episode 57: Pokémon VS Digimon (5:34)

Season 3
Episode 58: Bayonetta VS ???

Trivia

 * Yoshi vs Riptor is the shortest 2D fight.
 * Link vs Cloud is the shortest 3D fight.
 * Hercule Satan vs Dan Hibiki is the longest 2D fight.
 * Goku vs Superman is the longest 3D fight.