Since i think i'll have to rebalance the initial version of my character, could everyone please give me an idea of what you consider your own most powerful attack?

No need for any details, if you want to keep that secret, just a measure of said attack's strength, so i could know what the upper limit for my characters' durability should be. It's one of his major abilities, so i'd naturally want to tone it down as little as possible, unless there's a good reason to do otherwise.