If your oponent has some low life on a ninja and the battle is already won by him (battle already over) it will be fair to retreat before you have the chance to kill that ninja. Because some fair - play is required in this game as long as his strategy could be denied by that dead ninja ( reviving takes revival potions and moreover you can do it for only 3 ninjas) . So for fair - play that *on should remain there and in all PVP events in my opinion.