that is not really true about one piece. nami's mother was killed right infront her eyes. the other 49 ships of captain kreg fleet was killed by hawkeye. The octopus was killed by zoro. the priests were killed as well in the skypiea arc. Arlong is supposedly dead. The crew that sanji was with when he was a child is dead.
Also the pirate whats his name was also killed by the guy with the springy legs this was before the skypiea arc.
But i do get what you're saying. But Bleach is a little complicated since it has the whole soul society thing and all. But there have been deaths, if you count the hollow and if you count the people that turned into hollow; example orihime's brother. Also what about ichigo's mom, that is a big part of his character (it is what basically what changed his childhood). Zaraki killed ichinose's master. And Ishida's master and grandfather was also killed. Also what about all those souls that were absorbed by the bounto, do they not count as being dead....
In fact all the anime has death but just to different degree.