If you want to do Carina's that award 7* shards specifically, I think the only ones available are the most recent ones. Technically the "Complete Act 7 with 7*s" are available as well but if this is going to be your first 7*, then that's obviously off the table for now.
I don't see a 5* Stark Spidey in your roster but if you have him, I would focus on ranking him up in order to defeat either of the two Kang bosses in Act 7 with only him on the team. That's probably the easiest CC for you at this time.
If you don't have that 5* Starky, I would do my damnedest to get him and then do the challenge. I can't think of any other challenge that's easier, especially not that award 7* shards.
By the looks of your account you are only Throne breaker are there even any Carinas challenges available to you that have 7* shards. I would say push for Paragon and do the shooting stars quest if you want 7* champs
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I don't see a 5* Stark Spidey in your roster but if you have him, I would focus on ranking him up in order to defeat either of the two Kang bosses in Act 7 with only him on the team. That's probably the easiest CC for you at this time.
If you don't have that 5* Starky, I would do my damnedest to get him and then do the challenge. I can't think of any other challenge that's easier, especially not that award 7* shards.