Who to rank up

Looking for the best champion for bgs. I normally don't rank up 6*s but i don't know if someone is better. I would prefer it to be a 7*

6* r5 I have: Kate Bishop, Nick Fury, Aegon
7* r2 I have: Mantis, Attuma
7* r3 I have: Shang Chi

6* r5 I have: Kate Bishop, Nick Fury, Aegon
7* r2 I have: Mantis, Attuma
7* r3 I have: Shang Chi
Who to rank up 3 votes
0