Rank 4 Six star hypothetical

Silver Surfer, hands down. Partly due to prestige (he's at sig200 right now, so not ranking him up seems like a waste) but primarily because he's one of my favorite champs to play and I use him all the time.
Or maybe Void.

UnidentifiedCreature

I would rank 4 Karnak. I don't have a 6* Karnak at all, let alone at rank 3, but I would just love to see if at least a rank 4 Karnak could have semi-usable or decent damage output

GoddessIlias

Claire for practical usage, Corvus for alliance content, or Weapon X for flex value

Crcrcrc

Well, considering I don't have a r3 yet, it would probably go right to storage for a few months

yuw

apoc is the only r3 i got right now, maybe human torch in 1-2 months

Jackd1989

my only r3 at the moment is Warlock so would have to be him

Terra

Dr Strange.
I'm closing in every day on the r3. If a 3>4 rankup gem for 6*s ever drops, I'm bloody buying one

Polygon

Too bad those that swear by corvus are going to pretty much forced to make him the first r4, just so he stays relevant.