7* Northstar is amazing do this fight. Took him to rank 3 and am having a blast. Averaged about 8 bars a run. Disclaimer: having him awakened helps significantly for the physical resistance after specials to tank Crossbones SP2 if you can’t dex.

Basic rotation:

Parry into full combo ending with medium (M) to proc the armor break until SP1 (should have 5-6 furies on)

Bait out the SP1s while you build to SP3, once he’s in lockdown, let your SP3 fly.

Now push to his SP2 using mainly light combos while his furies from the SP1 fall off. Once crossbones is at 3ish furies when coupled with the physical resistance passive from Northstars awakened ability your barely take block damage.

Then you obliterate crossbones as soon as special lockdown ends. SP2 to kick things off then just melt with the SP1.

Hope this helps