Anyone, but Arnim
you really don’t need to rank anyone specific for crucibles. You just need a pretty health/diverse group of champs. R3s and whatnot make it easier but it’s really about picking the right counter for each fight, even if they are 7r1 or even r4 or r5 six stars.
For Necro, the most efficient options are probably still Shuri and Kate with a few key utility champs for synergies and specific fights.
There are tons of good YT guides for both pieces of content…
Shuri if you get her Awakened - her ability to block Unblockable specials is one of her key abilities in simplifying Necropolis fights.
If you've got her, Ironheart is amazing there, too.
Chee'ilth is brilliant there (and lots of other places)
I see Wong just off the edge of one slide - definitely him.
Odin is very good in Necropolis, too.
Onslaught is great for necro at r4