I imagined this achievement concerns only one playthrough otherwise it's pointless ...

But i done the playthrough 3 times already and i might have reloaded the game during a battle each time but i didn't loose any battle apart from 1.

As i imagine the battle on the bridge is quite unbeatable. So is there a way to avoid it ????

or to stuff the right character with the right item (tried that but even in easy this boss is a pure monster) ??

I'm doing a last playthrough in hard mode to get the 2 others achievement i lack, and kind of gave up on this one, as i saw on steam 0% of the players have it ......