exactlyHashi spared his life, obviously.
i think he fought tobirama not hashirama.
i think hashi, beat him in a fair fight and then kakazu retreated because he knew he couldn't beat/kill him
kakuzu basically became the biggest joke after yesterday's manga....i think i just figured out why he had so many stitches on his body......hashi basically shredded him to pieces and that's why he needed so many hearts to stay alive.....