I recorded all the bosses for a long boss rush in all the demos of Brutal Mario, sometimes it did require some manipulation of the code. This hack was made by Carol and has a good difficulty curve most of the time. Please take breaks in between for the sake of your sanity.

bosses:
1. Shy Guy
2. Lemmy Koopa
3. Big Boo
4. Mecha Mario
5. Morton Koopa Jr.
6. Mammon Machine
7. Kaptain K. Rool
8. Xan Bie
9. Wendy O. Koopa
10. Big Boo (2)
11. Boom Boom
12. Squawk
13. Iggy Koopa
14. Pumpkin Bombs
15. Dumb Drum
16. Fake Bowser
17. Wallface/Demon Wall
18. Big Boo (3)
19. Larry Koopa
20. Wiggler
21. Yellow Devil MK 2
22. Chomp Chomp
23. Whispy Woods
24. Kracko
25. King Dedede
26. Kirby
27. Wily Capsule
28. Koopa Bros
29. Roy Koopa
30. Lightgazer
31. Zable Fahr
32. Demon Wall
33. Ring Man
34. Ludwig Van Koopa
35. Reactor
36. Meta Knight
37. Ultima
38. Carmilla Queen
39. Archdemon
40. Black Rabbite
41. Dragon Lord
42. Gova/Gorva
43. Dark Lich
44. Lady Bow
45. Bowser (Final Boss 1)
46. 7 Koopalings Fusion (Final Boss 2)
47. Lemmy The Hikikomori (Demo 1)
48. Nova and Marx
49. Marx
50. Kirby (2)
51. Hanging Ghost
52. Quint
53. Mecha Dragon
54. Doc Robot (Cold Man)
55. Doc Robot (Flame Man)
56. Doc Robot (Wood Man)
57. Doc Robot (Bright Man)
58. Wily Machine and Capsule
59. Nightmare Power Orb
60. Ricardo Toad
61. Toad
62. Luigi (Final Boss 3)