I already give to sephiroth *4 cut/ death blow/ slash all, i only didnt give him a death animation because he dont have one.
To do this you have to go in the animation script of your character, located just after the model section , the model section = 68 bytes, it mean just after this you'll have the "offsets to animations script", it always start with "190" ( its 2 bytes or 4 bytes i dont remember) for playable characters, to calculate where is the first animation script you have to do "190+ offset to model section = the location of your very first animation script" ,which is the " standing" animation" ( 4 bytes) then the " hurt" animations and all the, what im calling, automatic animations, after all of them you'll have what i call the manual animations, the ones from your command list, attack, magic, summon,limit breaks, etc,i dont remember all but i writted a note when i was making the mod, with all the animations listing.
For example, here is a " double cut" animations script :
FC 02 03 F7 01 04 05 9E
FC 06 07 F7 01 08 09 E5 EE
I managed to find certain values with the wiki and i completed the rest by testing each codes one by one
FC = make your character look in the direction of the enemy you aimed
02 = second animation ( same for all other numbers like this so 03 is the third , 04 fourth, etc, most of attacks are the combinations of 4 animations)
F7 01= making the damage appear after one frame , when a number is following f7 its not an animation but the number of frame you wait after the damage will appear on the screen)
9E= used to link your first attack with another one, this is used for double cut, 4 cut, and tifa's limit breaks, for " combo"
E5= your character return to the default standing animation
EE= the end of your animation ,most of time you have a lot of space to make longer animations than the originals, but for characters with gunfire and many sounds, like dyne, you' are forced to enlarged a lot your animation script, by doing this you will 'erase" the next animation script, so you have to re write the new offset by doing : "offset to the animation script - model section offset = new offset of animation script"
This isnt simple, and my english is not perfect , dunno if you understand everything i said , lazy bastard havent detailled the animation scripts in his breakdown, but he give certains details in another post, which helped me to discover everthing about this (with the help of the wiki they decrypted certains animations codes)