I used a team consisting of zBossk (L), Boba, Jango, Cad Bane, and Dengar. I managed to do it with some solid mods and a specific kill order and a semi-specific turn order. It took a lot of tries and RNG, but what I eventually got to work was this:
1. Survive the initial onslaught, with either Dengar or Boba being stunned, and then Dengar becoming stealthed from Chewie’s AOE.
- If Boba was stunned, then sometimes it worked out better if he died outright so that he wouldn’t miss his turn.
2. Use Bossk’s taunt (first turn).
3. Use Jango’s first special on Lando so that he becomes the weakest enemy (second turn).
4. Use Bossk’s assist special on Lando, the weakest enemy, to work towards triggering the contract (third turn).
5. Use Cad Bane’s basic to finish off Lando if necessary (fourth turn).
6. Switch the target to Han, even if he’s not the weakest enemy. It should be Boba’s turn, and use his Execute ability to get some decent damage (because of Han’s buffs) and make Han the weakest character. Additionally, this should hopefully land a Healing Immunity (fifth turn).
7. From there, focus fire on Han, using the Fetts’ and Dengar’s AOEs to land debuffs and regain health and protection when possible.
8. Once Han is killed, start attacking Chewie, using Cad, Dengar, and Bossk to stun him.
9. After Chewie is killed, kill ROLO and then R2D2.
10. Enjoy your seven star Chewbacca and say a prayer of thanks to RNGesus.
*Disclaimer- This method has been known to induce strong emotions including, but not limited to: overwhelming rage, transcendent euphoria, crushing disappointment, burgeoning hopelessness, existential questioning, and complete and utter apathy towards all things, including life and everything that previously brought you joy.*