Who to R4?

Deepworld

I'm coming up on my first R4 as I'm just a few fragments away from some T6Bs and R3As so who should I rank up?

I want to R4 CGR but his damage output is already insane and I'm not sure if he'd benefit from the extra rank.

13579rebel_

Go with who you want

willrun4adonut

Apocalypse (unduped)

But if you run suicides, I'd say Corvus is a good contender too.