Hi, this is a guide that will hopefully work. I might make more guides like this depending on the feedback I get, idk, I just saw players struggling and wanted to try and help.
THE EVIL EMPEROR OF THE UNIVERSE GUIDE THINGY
The first and most important rule is you NEED a sealer and I mean it (Unless your on JP and can one-hit FP Freiza with SS4 Goku :P). Buutenks is your best bet but any sealer will do. The Pinnacle of Rage SS Goku could be a good replacement with the surviving K.O attacks and all but sealing is way more effective.
List of sealers <--- Go here if your wondering what units have the sealing ability
So with your sealer, you want to keep him in the 1st or 2nd spot AT ALL TIMES. Sealers seal the enemy's SA for 2 turns, so if he is in the 1st or 2nd spot, the sealer will return when FP Frieza is unsealed allowing for you to seal again.
I recommend having units that have + Ki link skills with your sealer so your sealer has a better chance of sealing.
Now for the leader I would say bring a +3 Ki lead because you should know why, yea, for your sealer but a +2 Ki lead should work just fine.
As for your other units, choose preferably STR types and choose your hardest hitting ones, if you don't have any hard-hitting STR types, then any type will do (except for INT of course). If you don't have any hard-hitters at all then try and find a Super Gogeta Friend or Omega Shenron, something along that nature. A stunner would also work great but you still want a sealer, stunning just makes the battle go more smoothly.
Tip: When you first begin the event and are on the map, take the cloud to the right and get the ? closest to the 2nd cloud, it might be a major coincidence but I always get +3 Ki on one of my units from that.
As for support items definitely take Korin's Herb Blend to cancel the Coercion which makes you unable to change attack order and take a Baba to reduce his SA to a normal attack, it helps when you can't get enough ki for your sealer to seal.
Thats pretty much it, I know this was a terrible guide but I hope it somehow helps you.