Use Omega lead and Omega friend and make sure to always super attack with them. Omega's SA greatly lowers the enemy defense, so after two SA everyone in your team will do damage to him making the fight an easy one. If you don't have Omega, and Omega friend only should do the trick as well.
Also, critical attack always do damage to Broly. So if you have characters with that skill make sure to use them.
Just replying to your comment again. A+ strategy for Broly's super stage!! I can take him down easily with a mixed team (Omega lead/friend, Gogeta, SuperVegito, SSBKK, and the video/FamilyGoten for a blazing battle link that helps sometimes). No items needed, and I'm well on my way to the 77 medals to awaken this bad boy! So thanks again!
New question-- what's the best team I have to take down Gotenks' raid? Gods are Omega, SV, and PHY Broly. Also have Gogeta/Janemba. I can post my full box later, but basically it's just those god/demigod cards. Tons of good STR units (SSJ3 Vegeta/Goku, Beerus, etc), some good PHY cards (Goku Black -- not awoken yet -- and Kid Buu). A lot of good AGL cards, but I think I tried mono-AGL SV before and it didn't go well
I need his medals to awaken my STR SSJ Gotenks card and start using the new dupe for him. Should make my Omega team hit even harder, but it's the only event I can't beat yet