Mutant R5 rankup help!

Got a 4-5 mutant rankup gem from completing 8.3. Torn on which champion to rankup. Here are my options...please ignore Domino/Bushop/StormX/Sunspot since I already have them as 7-stars.


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I ranked 5 my Apoc and it has been a treat to see him bossing most fights I used him in…
But Kitty is probably the smartest choice.
Only need the sinister relic now.