>>23381656
>>23381453
>I still don't understand how Arondight managed to get cut in half in the final battle
>>23381700
>>23381857

You are ovethinking it. The sword breaks because it's reached the limit of its durability just like in this webm. Athrun had been clashing their swords for a while. Knowing how crafty Athrun is, he probably hit a weak point or just kept smacking the same spot until it broke.