If you're asking whether you can do part-completion on each of 5 different characters and it will count as 1 total completion then yes you can, but you still have to get all the different parts at least once each.
For example each map has 6 delves and you need to do each of them once, it doesn't matter whether that's all on 1 character or across 2, 3, 4, 5 or 6 characters. But completing the same delve 6 times on 6 different characters will still only count once.
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