http://www.kongregate.com/games/danielsun/culmination

(not the most elegant solutions, but they work)
(also, because of the 'strange' mode differences in playable character, these will seem a bit odd)

take no damage from attacks:
normal:
a2 a1 68 ?? ?? 10 0b 00 00 d0 d0 66 ?? ?? 62 ?? a1 -> a2 a0 68 ?? ?? 10 0b 00 00 d0 d0 66 ?? ?? 62 ?? a0
d0 30 21 82 63 ?? 62 -> 47 30 21 82 63 ?? 62

hard:
63 ?? d0 66 ?? ?? 66 ?? ?? 96 -> 47 ?? d0 66 ?? ?? 66 ?? ?? 96

do more damage on boss level:
normal:
24 02 a3 a1 68 ?? ?? 10 28 -> 24 20 a2 a1 68 ?? ?? 10 28

hard:
29 00 00 d0 d0 66 ?? ?? 62 05 a1 -> 29 00 00 d0 d0 66 ?? ?? 24 7f a1

one hit kills on all but boss level:
62 ?? ?? ?? a3 a1 68 ?? ?? 10 0b 00 00 d0 d0 66 ?? ?? 62 ?? ->
02 02 02 24 7f a1 68 ?? ?? 10 0b 00 00 d0 d0 66 ?? ?? 24 7f